diff --git a/exercises/B-hello-world/exercise.js b/exercises/B-hello-world/exercise.js
index b179ee953..6815d627c 100644
--- a/exercises/B-hello-world/exercise.js
+++ b/exercises/B-hello-world/exercise.js
@@ -1 +1,14 @@
 console.log("Hello world");
+
+// Try to `console.log()` something different. For example, 'Hello World. I just started learning JavaScript!'.
+console.log("Hi, I'm Matilda, a software developer");
+
+// Try to console.log() several things at once.
+console.log("Hello " + "Everyone");
+console.log("CodeYourFuture is " + "AWESOME!!!");
+
+// What happens when you get rid of the quote marks? It reads it as a variable then throws an error that the variable hasn't been defined.
+// console.log(hello);
+
+// What happens when you console.log() just a number without quotes? It returns a number
+console.log(99);
\ No newline at end of file
diff --git a/exercises/C-variables/exercise.js b/exercises/C-variables/exercise.js
index a6bbb9786..f7d3dfca7 100644
--- a/exercises/C-variables/exercise.js
+++ b/exercises/C-variables/exercise.js
@@ -1,3 +1,5 @@
 // Start by creating a variable `greeting`
-
+let greeting = "Hello world";
 console.log(greeting);
+console.log(greeting);
+console.log(greeting);
\ No newline at end of file
diff --git a/exercises/D-strings/exercise.js b/exercises/D-strings/exercise.js
index 2cffa6a81..c08767a54 100644
--- a/exercises/D-strings/exercise.js
+++ b/exercises/D-strings/exercise.js
@@ -1,3 +1,4 @@
 // Start by creating a variable `message`
-
+let message = "I think coding is very fun";
 console.log(message);
+console.log(typeof message);
\ No newline at end of file
diff --git a/exercises/E-strings-concatenation/exercise.js b/exercises/E-strings-concatenation/exercise.js
index 2cffa6a81..d4c746914 100644
--- a/exercises/E-strings-concatenation/exercise.js
+++ b/exercises/E-strings-concatenation/exercise.js
@@ -1,3 +1,4 @@
 // Start by creating a variable `message`
-
-console.log(message);
+let message = "Hey there, it's nice to meet you, I'm ";
+let name = "Matilda";
+console.log(message + name);
\ No newline at end of file
diff --git a/exercises/F-strings-methods/exercise.js b/exercises/F-strings-methods/exercise.js
index 2cffa6a81..1646c09a2 100644
--- a/exercises/F-strings-methods/exercise.js
+++ b/exercises/F-strings-methods/exercise.js
@@ -1,3 +1,5 @@
 // Start by creating a variable `message`
-
-console.log(message);
+let name = "Matilda";
+let length = name.length;
+let message = `Hi, I'm ${name}, ${name} has ${length} characters in it`;
+console.log(message);
\ No newline at end of file
diff --git a/exercises/F-strings-methods/exercise2.js b/exercises/F-strings-methods/exercise2.js
index b4b46943d..d8a91442a 100644
--- a/exercises/F-strings-methods/exercise2.js
+++ b/exercises/F-strings-methods/exercise2.js
@@ -1,3 +1,3 @@
 const name = " Daniel  ";
-
-console.log(message);
+let message = `My name is ${name.trim()} and my name is 6 characters long`;
+console.log(message);
\ No newline at end of file
diff --git a/exercises/G-numbers/exercise.js b/exercises/G-numbers/exercise.js
index 49e7bc00b..83c5bf9f3 100644
--- a/exercises/G-numbers/exercise.js
+++ b/exercises/G-numbers/exercise.js
@@ -1 +1,7 @@
 // Start by creating a variables `numberOfStudents` and `numberOfMentors`
+let numberOfStudents = 15;
+let numberOfMentors = 8;
+let message = `Number of students: ${numberOfStudents}
+Number of mentors: ${numberOfMentors}
+Total number of students and mentors: ${numberOfStudents + numberOfMentors}`;
+console.log(message);
\ No newline at end of file
diff --git a/exercises/I-floats/exercise.js b/exercises/I-floats/exercise.js
index a5bbcd852..d899e2e16 100644
--- a/exercises/I-floats/exercise.js
+++ b/exercises/I-floats/exercise.js
@@ -1,2 +1,13 @@
 var numberOfStudents = 15;
 var numberOfMentors = 8;
+
+let totalNumber = numberOfStudents + numberOfMentors;
+let studentPercentage = Math.round((numberOfStudents / totalNumber) * 100);
+let mentorPercentage = Math.round((numberOfMentors / totalNumber) * 100);
+
+let numbers = `Percentage students: ${studentPercentage}%
+Percentage mentors: ${mentorPercentage}%`;
+
+console.log(numbers);
+// Percentage students: 65%
+// Percentage mentors: 35%
\ No newline at end of file
diff --git a/exercises/J-functions/exercise.js b/exercises/J-functions/exercise.js
index 0ae5850e5..ecf1ad765 100644
--- a/exercises/J-functions/exercise.js
+++ b/exercises/J-functions/exercise.js
@@ -1,7 +1,11 @@
 function halve(number) {
-  // complete the function here
+    // complete the function here
+    return number / 2;
 }
 
 var result = halve(12);
 
 console.log(result);
+console.log(halve(79));
+console.log(halve(8990));
+console.log(halve(787979323));
\ No newline at end of file
diff --git a/exercises/J-functions/exercise2.js b/exercises/J-functions/exercise2.js
index 82ef5e780..1448382f3 100644
--- a/exercises/J-functions/exercise2.js
+++ b/exercises/J-functions/exercise2.js
@@ -1,7 +1,8 @@
 function triple(number) {
-  // complete function here
+    // complete function here
+    return number * 3;
 }
 
 var result = triple(12);
 
-console.log(result);
+console.log(result);
\ No newline at end of file
diff --git a/exercises/K-functions-parameters/exercise.js b/exercises/K-functions-parameters/exercise.js
index 8d5db5e69..d74aa8044 100644
--- a/exercises/K-functions-parameters/exercise.js
+++ b/exercises/K-functions-parameters/exercise.js
@@ -1,9 +1,10 @@
 // Complete the function so that it takes input parameters
-function multiply() {
-  // Calculate the result of the function and return it
+function multiply(a, b) {
+    // Calculate the result of the function and return it
+    return a * b;
 }
 
 // Assign the result of calling the function the variable `result`
 var result = multiply(3, 4);
 
-console.log(result);
+console.log(result);
\ No newline at end of file
diff --git a/exercises/K-functions-parameters/exercise2.js b/exercises/K-functions-parameters/exercise2.js
index db7a8904b..b76badfd6 100644
--- a/exercises/K-functions-parameters/exercise2.js
+++ b/exercises/K-functions-parameters/exercise2.js
@@ -1,5 +1,8 @@
 // Declare your function first
+function divide(a, b) {
+    return a / b;
+}
 
 var result = divide(3, 4);
 
-console.log(result);
+console.log(result);
\ No newline at end of file
diff --git a/exercises/K-functions-parameters/exercise3.js b/exercises/K-functions-parameters/exercise3.js
index 537e9f4ec..4ba32b475 100644
--- a/exercises/K-functions-parameters/exercise3.js
+++ b/exercises/K-functions-parameters/exercise3.js
@@ -1,5 +1,8 @@
 // Write your function here
+function createGreeting(name) {
+    return `Hello, my name is ${name}`;
+}
 
 var greeting = createGreeting("Daniel");
 
-console.log(greeting);
+console.log(greeting);
\ No newline at end of file
diff --git a/exercises/K-functions-parameters/exercise4.js b/exercises/K-functions-parameters/exercise4.js
index 7ab44589e..6d266e381 100644
--- a/exercises/K-functions-parameters/exercise4.js
+++ b/exercises/K-functions-parameters/exercise4.js
@@ -1,5 +1,8 @@
 // Declare your function first
+function sumOfNumbers(num1, num2) {
+    return num1 + num2;
+}
 
 // Call the function and assign to a variable `sum`
-
-console.log(sum);
+let sum = sumOfNumbers(13, 124);
+console.log(sum);
\ No newline at end of file
diff --git a/exercises/K-functions-parameters/exercise5.js b/exercises/K-functions-parameters/exercise5.js
index 7c5bcd605..92692754b 100644
--- a/exercises/K-functions-parameters/exercise5.js
+++ b/exercises/K-functions-parameters/exercise5.js
@@ -1,5 +1,7 @@
 // Declare your function here
-
+function createLongGreeting(name, age) {
+    return "Hello, my name is " + name + " and I'm " + age + " years old";
+}
 const greeting = createLongGreeting("Daniel", 30);
-
-console.log(greeting);
+// Hello, my name is Daniel and I'm 30 years old
+console.log(greeting);
\ No newline at end of file
diff --git a/exercises/L-functions-nested/README.md b/exercises/L-functions-nested/README.md
index 1c4ae9c8a..012be64e0 100644
--- a/exercises/L-functions-nested/README.md
+++ b/exercises/L-functions-nested/README.md
@@ -9,7 +9,7 @@ function getAgeInDays(age) {
   return age * 365;
 }
 
-function createCreeting(name, age) {
+function createGreeting(name, age) {
   var ageInDays = getAgeInDays(age);
   var message =
     "My Name is " + name + " and I was born over " + ageInDays + " days ago!";
diff --git a/exercises/L-functions-nested/exercise.js b/exercises/L-functions-nested/exercise.js
index a5d377442..aa5d742b7 100644
--- a/exercises/L-functions-nested/exercise.js
+++ b/exercises/L-functions-nested/exercise.js
@@ -3,3 +3,18 @@ var mentor2 = "Irina";
 var mentor3 = "Mimi";
 var mentor4 = "Rob";
 var mentor5 = "Yohannes";
+
+function upperCaseNames(mentor) {
+    return mentor.toUpperCase();
+}
+
+function shoutyGreeting(mentor) {
+    var name = upperCaseNames(mentor);
+    return "HELLO " + name;
+}
+
+console.log(shoutyGreeting(mentor1));
+console.log(shoutyGreeting(mentor2));
+console.log(shoutyGreeting(mentor3));
+console.log(shoutyGreeting(mentor4));
+console.log(shoutyGreeting(mentor5));
\ No newline at end of file
diff --git a/extra/1-currency-conversion.js b/extra/1-currency-conversion.js
index d82e59480..b46871d61 100644
--- a/extra/1-currency-conversion.js
+++ b/extra/1-currency-conversion.js
@@ -5,7 +5,9 @@
   Write a function that converts a price to USD (exchange rate is 1.4 $ to £)
 */
 
-function convertToUSD() {}
+function convertToUSD(price) {
+    return price * 1.4;
+}
 
 /*
   CURRENCY CONVERSION
@@ -15,27 +17,30 @@ function convertToUSD() {}
   They have also decided that they should add a 1% fee to all foreign transactions, which means you only convert 99% of the £ to BRL.
 */
 
-function convertToBRL() {}
+function convertToBRL(price) {
+    let num = (price / 100) * 99 * 5.7; //converts £ to brl
+    return Math.round(num * 100 + Number.EPSILON) / 100; //returns the value as a 2dp number
+}
 
 /* ======= TESTS - DO NOT MODIFY ===== 
 There are some Tests in this file that will help you work out if your code is working.
 
-To run these tests type `npm run extraTo run the tests for just this one file, type `npm run extra-tests -- --testPathPattern 1-syntax-errors` into your terminal
+To run the tests for just this one file, type `npm test -- --testPathPattern 1-currency-conversion` into your terminal
 (Reminder: You must have run `npm install` one time before this will work!)
 */
 
 test("convertToUSD function works for £32", () => {
-  expect(convertToUSD(32)).toEqual(44.8);
+    expect(convertToUSD(32)).toEqual(44.8);
 });
 
 test("convertToUSD function works for £50", () => {
-  expect(convertToUSD(50)).toEqual(70);
+    expect(convertToUSD(50)).toEqual(70);
 });
 
 test("convertToBRL function works for £30", () => {
-  expect(convertToBRL(30)).toEqual(169.29);
+    expect(convertToBRL(30)).toEqual(169.29);
 });
 
 test("convertToBRL function works for £1.50", () => {
-  expect(convertToBRL(1.5)).toEqual(8.46);
-});
+    expect(convertToBRL(1.5)).toEqual(8.46);
+});
\ No newline at end of file
diff --git a/extra/2-piping.js b/extra/2-piping.js
index 9c8ebc76a..dc316b635 100644
--- a/extra/2-piping.js
+++ b/extra/2-piping.js
@@ -16,27 +16,27 @@
   the final result to the variable goodCode
 */
 
-function add() {
-
+function add(a, b) {
+    return a + b;
 }
 
-function multiply() {
-
+function multiply(a, b) {
+    return a * b;
 }
 
-function format() {
-
+function format(num) {
+    return "£" + num;
 }
 
 const startingValue = 2;
 
 // Why can this code be seen as bad practice? Comment your answer.
-let badCode =
+let badCode = format(multiply(add(startingValue, 10), 2));
 
 /* BETTER PRACTICE */
-
-let goodCode =
-
+let sum = add(startingValue, 10);
+let times = multiply(sum, 2);
+let goodCode = format(times);
 /* ======= TESTS - DO NOT MODIFY ===== 
 There are some Tests in this file that will help you work out if your code is working.
 
@@ -45,29 +45,29 @@ To run these tests type `npm run extraTo run the tests for just this one file, t
 */
 
 test("add function - case 1 works", () => {
-  expect(add(1, 3)).toEqual(4);
+    expect(add(1, 3)).toEqual(4);
 });
 
 test("add function - case 2 works", () => {
-  expect(add(2.4, 5)).toEqual(7.4);
+    expect(add(2.4, 5)).toEqual(7.4);
 });
 
 test("multiply function works", () => {
-  expect(multiply(2, 3)).toEqual(6);
+    expect(multiply(2, 3)).toEqual(6);
 });
 
 test("format function works for whole number", () => {
-  expect(format(16)).toEqual("£16");
+    expect(format(16)).toEqual("£16");
 });
 
 test("format function works for decimal number", () => {
-  expect(format(10.1)).toEqual("£10.1");
+    expect(format(10.1)).toEqual("£10.1");
 });
 
 test("badCode variable correctly assigned", () => {
-  expect(badCode).toEqual("£24");
+    expect(badCode).toEqual("£24");
 });
 
 test("goodCode variable correctly assigned", () => {
-  expect(goodCode).toEqual("£24");
-});
+    expect(goodCode).toEqual("£24");
+});
\ No newline at end of file
diff --git a/extra/3-magic-8-ball.js b/extra/3-magic-8-ball.js
index f3adbefa5..e2e70b9c6 100644
--- a/extra/3-magic-8-ball.js
+++ b/extra/3-magic-8-ball.js
@@ -1,3 +1,5 @@
+const matchers = require("jest-extended");
+expect.extend(matchers);
 /**
 
   Let's peer into the future using a Magic 8 Ball!
@@ -43,10 +45,54 @@
     Very doubtful.
 */
 
+let answers = {
+    veryPositive: [
+        "It is certain.",
+        "It is decidedly so.",
+        "Without a doubt.",
+        "Yes - definitely.",
+        "You may rely on it.",
+    ],
+    positive: [
+        "As I see it, yes.",
+        "Most likely.",
+        "Outlook good.",
+        "Yes.",
+        "Signs point to yes.",
+    ],
+
+    negative: [
+        "Reply hazy, try again.",
+        "Ask again later.",
+        "Better not tell you now.",
+        "Cannot predict now.",
+        "Concentrate and ask again.",
+    ],
+    veryNegative: [
+        "Don't count on it.",
+        "My reply is no.",
+        "My sources say no.",
+        "Outlook not so good.",
+        "Very doubtful.",
+    ],
+};
+
 // This should log "The ball has shaken!"
 // and return the answer.
 function shakeBall() {
-  //Write your code in here
+    //Write your code in here
+    let positivity = Math.floor(Math.random() * 4); // random number between 0 and 4 - the possible outcomes for veryPositive - veryNegative
+    let possibleAnswers = Math.floor(Math.random() * 5); // random number between 0 and 5 - the possible outcomes for each possible answer from the arrays veryPositive - veryNegative
+    console.log("The ball has shaken!");
+    if (positivity === 0) {
+        return answers.veryPositive[possibleAnswers];
+    } else if (positivity === 1) {
+        return answers.positive[possibleAnswers];
+    } else if (positivity === 2) {
+        return answers.negative[possibleAnswers];
+    } else if (positivity === 3) {
+        return answers.veryNegative[possibleAnswers];
+    }
 }
 
 /* 
@@ -59,7 +105,16 @@ function shakeBall() {
   This function should expect to be called with any value which was returned by the shakeBall function.
 */
 function checkAnswer(answer) {
-  //Write your code in here
+    //Write your code in here
+    if (answers.veryPositive.includes(answer)) {
+        return "very positive";
+    } else if (answers.positive.includes(answer)) {
+        return "positive";
+    } else if (answers.negative.includes(answer)) {
+        return "negative";
+    } else if (answers.veryNegative.includes(answer)) {
+        return "very negative";
+    }
 }
 
 /* 
@@ -74,45 +129,47 @@ To run these tests type `npm run extraTo run the tests for just this one file, t
 */
 
 test("whole magic 8 ball sequence", () => {
-  const consoleLogSpy = jest.spyOn(global.console, "log");
-  const answer = shakeBall();
+    const consoleLogSpy = jest.spyOn(global.console, "log");
+    const answer = shakeBall();
 
-  expect(typeof answer).toEqual("string");
+    expect(typeof answer).toEqual("string");
 
-  expect(consoleLogSpy).toHaveBeenCalledTimes(1);
-  expect(consoleLogSpy).toHaveBeenLastCalledWith("The ball has shaken!");
+    expect(consoleLogSpy).toHaveBeenCalledTimes(1);
+    expect(consoleLogSpy).toHaveBeenLastCalledWith("The ball has shaken!");
 
-  expect(checkAnswer(answer)).toBeOneOf([
-    "very positive",
-    "positive",
-    "negative",
-    "very negative",
-  ]);
+    expect(checkAnswer(answer)).toBeOneOf([
+        "very positive",
+        "positive",
+        "negative",
+        "very negative",
+    ]);
 });
 
 test("magic 8 ball returns different values each time", () => {
-  const seenAnswers = new Set();
-  for (let i = 0; i < 10; ++i) {
-    seenAnswers.add(shakeBall());
-  }
-  if (seenAnswers.size < 2) {
-    throw Error(
-      "Expected to get different random answers each time shakeBall was called, but always got the same one"
-    );
-  }
-
-  let seenPositivities = new Set(Array.from(seenAnswers.values()).map(checkAnswer));
-  if (seenPositivities.size < 2) {
-    throw Error(
-      "Expected to random answers with different positivities each time shakeBall was called, but always got the same one"
+    const seenAnswers = new Set();
+    for (let i = 0; i < 10; ++i) {
+        seenAnswers.add(shakeBall());
+    }
+    if (seenAnswers.size < 2) {
+        throw Error(
+            "Expected to get different random answers each time shakeBall was called, but always got the same one"
+        );
+    }
+
+    let seenPositivities = new Set(
+        Array.from(seenAnswers.values()).map(checkAnswer)
     );
-  }
+    if (seenPositivities.size < 2) {
+        throw Error(
+            "Expected to random answers with different positivities each time shakeBall was called, but always got the same one"
+        );
+    }
 });
 
 test("checkAnswer works for `It is decidedly so.`", () => {
-  expect(checkAnswer("It is decidedly so.")).toEqual("very positive");
+    expect(checkAnswer("It is decidedly so.")).toEqual("very positive");
 });
 
 test("checkAnswer works for `My reply is no.`", () => {
-  expect(checkAnswer("My reply is no.")).toEqual("very negative");
-});
+    expect(checkAnswer("My reply is no.")).toEqual("very negative");
+});
\ No newline at end of file
diff --git a/mandatory/1-syntax-errors.js b/mandatory/1-syntax-errors.js
index a10cc9ac2..f50ef9dc3 100644
--- a/mandatory/1-syntax-errors.js
+++ b/mandatory/1-syntax-errors.js
@@ -1,16 +1,17 @@
 // There are syntax errors in this code - can you fix it to pass the tests?
 
-function addNumbers(a b c) {
-  return a + b + c;
+function addNumbers(a, b, c) {
+    return a + b + c;
 }
 
-function introduceMe(name, age)
-  return "Hello, my name is " + name "and I am " age + "years old";
+function introduceMe(name, age) {
+    return "Hello, my name is " + name + " and I am " + age + " years old";
+}
 
 function getTotal(a, b) {
-  total = a ++ b;
+    total = a + b;
 
-  return "The total is total";
+    return "The total is " + total;
 }
 
 /* 
@@ -26,15 +27,15 @@ To run the tests for just this one file, type `npm test -- --testPathPattern 1-s
 */
 
 test("addNumbers adds numbers correctly", () => {
-  expect(addNumbers(3, 4, 6)).toEqual(13);
+    expect(addNumbers(3, 4, 6)).toEqual(13);
 });
 
 test("introduceMe function returns the correct string", () => {
-  expect(introduceMe("Sonjide", 27)).toEqual(
-    "Hello, my name is Sonjide and I am 27 years old"
-  );
+    expect(introduceMe("Sonjide", 27)).toEqual(
+        "Hello, my name is Sonjide and I am 27 years old"
+    );
 });
 
 test("getTotal returns a string describing the total", () => {
-  expect(getTotal(23, 5)).toEqual("The total is 28");
-});
+    expect(getTotal(23, 5)).toEqual("The total is 28");
+});
\ No newline at end of file
diff --git a/mandatory/2-logic-error.js b/mandatory/2-logic-error.js
index 9cca7603b..a9632a6ff 100644
--- a/mandatory/2-logic-error.js
+++ b/mandatory/2-logic-error.js
@@ -1,16 +1,15 @@
 // The syntax for this function is valid but it has an error, find it and fix it.
 
 function trimWord(word) {
-  return wordtrim();
+    return word.trim();
 }
 
 function getStringLength(word) {
-  return "word".length();
+    return word.length;
 }
 
 function multiply(a, b, c) {
-  a * b * c;
-  return;
+    return a * b * c;
 }
 
 /* 
@@ -25,27 +24,27 @@ To run the tests for just this one file, type `npm test -- --testPathPattern 2-l
 */
 
 test("trimWord trims leading and trailing whitespace", () => {
-  expect(trimWord("   CodeYourFuture ")).toEqual("CodeYourFuture");
+    expect(trimWord("   CodeYourFuture ")).toEqual("CodeYourFuture");
 });
 
 test("trimWord doesn't remove whitespace in the middle of the string", () => {
-  expect(trimWord(" CodeYourFuture teaches coding     ")).toEqual(
-    "CodeYourFuture teaches coding"
-  );
+    expect(trimWord(" CodeYourFuture teaches coding     ")).toEqual(
+        "CodeYourFuture teaches coding"
+    );
 });
 
 test("getStringLength returns the length of a word", () => {
-  expect(getStringLength("Turtles")).toEqual(7);
+    expect(getStringLength("Turtles")).toEqual(7);
 });
 
 test("getStringLength returns the length of a sentence", () => {
-  expect(getStringLength("A wild sentence appeared!")).toEqual(25);
+    expect(getStringLength("A wild sentence appeared!")).toEqual(25);
 });
 
 test("multiply multiplies numbers", () => {
-  expect(multiply(2, 3, 6)).toEqual(36);
+    expect(multiply(2, 3, 6)).toEqual(36);
 });
 
 test("multiply multiplies different numbers", () => {
-  expect(multiply(2, 3, 4)).toEqual(24);
-});
+    expect(multiply(2, 3, 4)).toEqual(24);
+});
\ No newline at end of file
diff --git a/mandatory/3-function-output.js b/mandatory/3-function-output.js
index 5a953ba60..45907a6b4 100644
--- a/mandatory/3-function-output.js
+++ b/mandatory/3-function-output.js
@@ -1,16 +1,21 @@
 // Add comments to explain what this function does. You're meant to use Google!
+
+//This function creates a random number, random numbers are between 0 and 1 so multiplying it by 10 gives a random number between 0 (included) and 10 (not included)
 function getRandomNumber() {
-  return Math.random() * 10;
+    return Math.random() * 10;
 }
 
 // Add comments to explain what this function does. You're meant to use Google!
+
+//This function puts 2 words together to make one new word which will look like "word1word2"
 function combine2Words(word1, word2) {
-  return word1.concat(word2);
+    return word1.concat(word2);
 }
 
 function concatenate(firstWord, secondWord, thirdWord) {
-  // Write the body of this function to concatenate three words together.
-  // Look at the test case below to understand what this function is expected to return.
+    // Write the body of this function to concatenate three words together.
+    // Look at the test case below to understand what this function is expected to return.
+    return firstWord + " " + secondWord + " " + thirdWord;
 }
 
 /* 
@@ -25,13 +30,13 @@ To run the tests for just this one file, type `npm test -- --testPathPattern 3-f
 */
 
 test("concatenate example #1", () => {
-  expect(concatenate("code", "your", "future")).toEqual("code your future");
+    expect(concatenate("code", "your", "future")).toEqual("code your future");
 });
 
 test("concatenate example #2", () => {
-  expect(concatenate("I", "like", "pizza")).toEqual("I like pizza");
+    expect(concatenate("I", "like", "pizza")).toEqual("I like pizza");
 });
 
 test("concatenate doesn't only accept strings", () => {
-  expect(concatenate("I", "am", 13)).toEqual("I am 13");
-});
+    expect(concatenate("I", "am", 13)).toEqual("I am 13");
+});
\ No newline at end of file
diff --git a/mandatory/4-tax.js b/mandatory/4-tax.js
index ba77c7ae2..b73bc1448 100644
--- a/mandatory/4-tax.js
+++ b/mandatory/4-tax.js
@@ -5,7 +5,9 @@
   Sales tax is 20% of the price of the product.
 */
 
-function calculateSalesTax() {}
+function calculateSalesTax(price) {
+    return price + (price / 100) * 20;
+}
 
 /*
   CURRENCY FORMATTING
@@ -17,7 +19,10 @@ function calculateSalesTax() {}
   Remember that the prices must include the sales tax (hint: you already wrote a function for this!)
 */
 
-function addTaxAndFormatCurrency() {}
+function addTaxAndFormatCurrency(price) {
+    let priceWithTax = calculateSalesTax(price);
+    return `£${priceWithTax.toFixed(2, 0)}`;
+}
 
 /* 
 ===================================================
@@ -31,25 +36,25 @@ To run the tests for just this one file, type `npm test -- --testPathPattern 4-t
 */
 
 test("calculateSalesTax for £15", () => {
-  expect(calculateSalesTax(15)).toEqual(18);
+    expect(calculateSalesTax(15)).toEqual(18);
 });
 
 test("calculateSalesTax for £17.50", () => {
-  expect(calculateSalesTax(17.5)).toEqual(21);
+    expect(calculateSalesTax(17.5)).toEqual(21);
 });
 
 test("calculateSalesTax for £34", () => {
-  expect(calculateSalesTax(34)).toEqual(40.8);
+    expect(calculateSalesTax(34)).toEqual(40.8);
 });
 
 test("addTaxAndFormatCurrency for £15", () => {
-  expect(addTaxAndFormatCurrency(15)).toEqual("£18.00");
+    expect(addTaxAndFormatCurrency(15)).toEqual("£18.00");
 });
 
 test("addTaxAndFormatCurrency for £17.50", () => {
-  expect(addTaxAndFormatCurrency(17.5)).toEqual("£21.00");
+    expect(addTaxAndFormatCurrency(17.5)).toEqual("£21.00");
 });
 
 test("addTaxAndFormatCurrency for £34", () => {
-  expect(addTaxAndFormatCurrency(34)).toEqual("£40.80");
-});
+    expect(addTaxAndFormatCurrency(34)).toEqual("£40.80");
+});
\ No newline at end of file
diff --git a/package.json b/package.json
index 93e0861e3..118be12fa 100644
--- a/package.json
+++ b/package.json
@@ -1,34 +1,41 @@
 {
-  "name": "javascript-core-1-coursework-week1",
-  "version": "1.0.0",
-  "description": "Exercises for JS1 Week 1",
-  "license": "CC-BY-SA-4.0",
-  "scripts": {
-    "test": "jest"
-  },
-  "repository": {
-    "type": "git",
-    "url": "git+https://github.com/CodeYourFuture/JavaScript-Core-1-Coursework-Week1.git"
-  },
-  "bugs": {
-    "url": "https://github.com/CodeYourFuture/JavaScript-Core-1-Coursework-Week1/issues"
-  },
-  "jest": {
-    "setupFilesAfterEnv": ["jest-extended"],
-    "projects": [
-      {
-        "displayName": "mandatory",
-        "testMatch": ["<rootDir>/mandatory/*.js"]
-      },
-      {
-        "displayName": "extra",
-        "testMatch": ["<rootDir>/extra/*.js"]
-      }
-    ]
-  },
-  "homepage": "https://github.com/CodeYourFuture/JavaScript-Core-1-Coursework-Week1#readme",
-  "devDependencies": {
-    "jest": "^26.6.3",
-    "jest-extended": "^0.11.5"
-  }
+    "name": "javascript-core-1-coursework-week1",
+    "version": "1.0.0",
+    "description": "Exercises for JS1 Week 1",
+    "license": "CC-BY-SA-4.0",
+    "scripts": {
+        "test": "jest",
+        "extra-tests": "jest extra"
+    },
+    "repository": {
+        "type": "git",
+        "url": "git+https://github.com/CodeYourFuture/JavaScript-Core-1-Coursework-Week1.git"
+    },
+    "bugs": {
+        "url": "https://github.com/CodeYourFuture/JavaScript-Core-1-Coursework-Week1/issues"
+    },
+    "jest": {
+        "setupFilesAfterEnv": [
+            "jest-extended/all"
+        ],
+        "projects": [
+            {
+                "displayName": "mandatory",
+                "testMatch": [
+                    "<rootDir>/mandatory/*.js"
+                ]
+            },
+            {
+                "displayName": "extra",
+                "testMatch": [
+                    "<rootDir>/extra/*.js"
+                ]
+            }
+        ]
+    },
+    "homepage": "https://github.com/CodeYourFuture/JavaScript-Core-1-Coursework-Week1#readme",
+    "devDependencies": {
+        "jest": "^26.6.3",
+        "jest-extended": "^1.2.0"
+    }
 }