diff --git a/exercises/B-hello-world/README.md b/exercises/B-hello-world/README.md
index 8c704fb43..8eaf8f0e3 100644
--- a/exercises/B-hello-world/README.md
+++ b/exercises/B-hello-world/README.md
@@ -15,4 +15,6 @@ Inside of `exercise.js` there's a line of code that will print "Hello world!".
 - Try to `console.log()` something different. For example, 'Hello World. I just started learning JavaScript!'.
 - Try to console.log() several things at once.
 - What happens when you get rid of the quote marks?
+  We get a syntax error. SyntaxError: missing ) after argument list
 - What happens when you console.log() just a number without quotes?
+  It logs a number to the console. Numbers are not like strings. They do not need quotes around them. Otherwise, they would turn into a string.
diff --git a/exercises/B-hello-world/exercise.js b/exercises/B-hello-world/exercise.js
index b179ee953..9d4ad15fc 100644
--- a/exercises/B-hello-world/exercise.js
+++ b/exercises/B-hello-world/exercise.js
@@ -1 +1,3 @@
 console.log("Hello world");
+console.log("Hello World. I just started learning JavaScript!");
+console.log(12);
diff --git a/exercises/C-variables/exercise.js b/exercises/C-variables/exercise.js
index a6bbb9786..c2925e716 100644
--- a/exercises/C-variables/exercise.js
+++ b/exercises/C-variables/exercise.js
@@ -1,3 +1,6 @@
 // Start by creating a variable `greeting`
+const greeting = "Hello world";
 
 console.log(greeting);
+console.log(greeting);
+console.log(greeting);
diff --git a/exercises/D-strings/exercise.js b/exercises/D-strings/exercise.js
index 2cffa6a81..713063b08 100644
--- a/exercises/D-strings/exercise.js
+++ b/exercises/D-strings/exercise.js
@@ -1,3 +1,6 @@
 // Start by creating a variable `message`
+const myMessage = "Hi, I am Humail";
+const myMessageType = typeof myMessage;
 
-console.log(message);
+console.log(myMessage);
+console.log(myMessageType);
diff --git a/exercises/E-strings-concatenation/exercise.js b/exercises/E-strings-concatenation/exercise.js
index 2cffa6a81..5062e0274 100644
--- a/exercises/E-strings-concatenation/exercise.js
+++ b/exercises/E-strings-concatenation/exercise.js
@@ -1,3 +1,7 @@
 // Start by creating a variable `message`
+const greetingPartOne = "Hi, my name is ";
+const firstName = "Humail";
 
-console.log(message);
+const greetingConcatenated = greetingPartOne + firstName;
+
+console.log(greetingConcatenated);
diff --git a/exercises/F-strings-methods/exercise.js b/exercises/F-strings-methods/exercise.js
index 2cffa6a81..d651b333d 100644
--- a/exercises/F-strings-methods/exercise.js
+++ b/exercises/F-strings-methods/exercise.js
@@ -1,3 +1,11 @@
 // Start by creating a variable `message`
+const firstName = "Humail";
+const lengthOfMyName = firstName.length;
+const message =
+  "My name is " +
+  firstName +
+  " and my name is " +
+  lengthOfMyName +
+  " characters long.";
 
-console.log(message);
+console.log(message.trim());
diff --git a/exercises/F-strings-methods/exercise2.js b/exercises/F-strings-methods/exercise2.js
index b4b46943d..f8bcad671 100644
--- a/exercises/F-strings-methods/exercise2.js
+++ b/exercises/F-strings-methods/exercise2.js
@@ -1,3 +1,10 @@
 const name = " Daniel  ";
+const lengthOfMyName = name.trim().length;
+const message =
+  "My name is " +
+  name +
+  " and my name is " +
+  lengthOfMyName +
+  " characters long.";
 
 console.log(message);
diff --git a/exercises/G-numbers/exercise.js b/exercises/G-numbers/exercise.js
index 49e7bc00b..6f740f72e 100644
--- a/exercises/G-numbers/exercise.js
+++ b/exercises/G-numbers/exercise.js
@@ -1 +1,8 @@
 // Start by creating a variables `numberOfStudents` and `numberOfMentors`
+const numberOfStudents = 15;
+const numberOfMentors = 8;
+const totalNumbers = numberOfStudents + numberOfMentors;
+
+console.log(`Number of students: ${numberOfStudents}`);
+console.log(`Number of mentors: ${numberOfMentors}`);
+console.log(`Total number of students and mentors: ${totalNumbers}`);
diff --git a/exercises/I-floats/exercise.js b/exercises/I-floats/exercise.js
index a5bbcd852..3831e6ff8 100644
--- a/exercises/I-floats/exercise.js
+++ b/exercises/I-floats/exercise.js
@@ -1,2 +1,8 @@
 var numberOfStudents = 15;
 var numberOfMentors = 8;
+let totalNumbers = numberOfStudents + numberOfMentors;
+let percentageStudents = (numberOfStudents / totalNumbers) * 100;
+let percentageMentors = (numberOfMentors / totalNumbers) * 100;
+
+console.log(`Percentage students: ${Math.round(percentageStudents)}%`);
+console.log(`Percentage mentors: ${Math.round(percentageMentors)}%`);
diff --git a/exercises/J-functions/exercise.js b/exercises/J-functions/exercise.js
index 0ae5850e5..aa2ca8f2c 100644
--- a/exercises/J-functions/exercise.js
+++ b/exercises/J-functions/exercise.js
@@ -1,7 +1,12 @@
 function halve(number) {
   // complete the function here
+  return number / 2;
 }
 
 var result = halve(12);
 
 console.log(result);
+
+let resultTwo = halve(19);
+
+console.log(resultTwo);
diff --git a/exercises/J-functions/exercise2.js b/exercises/J-functions/exercise2.js
index 82ef5e780..468d45596 100644
--- a/exercises/J-functions/exercise2.js
+++ b/exercises/J-functions/exercise2.js
@@ -1,5 +1,6 @@
 function triple(number) {
   // complete function here
+  return number * 3;
 }
 
 var result = triple(12);
diff --git a/exercises/K-functions-parameters/exercise.js b/exercises/K-functions-parameters/exercise.js
index 8d5db5e69..a4eed9d76 100644
--- a/exercises/K-functions-parameters/exercise.js
+++ b/exercises/K-functions-parameters/exercise.js
@@ -1,6 +1,7 @@
 // Complete the function so that it takes input parameters
-function multiply() {
+function multiply(num1, num2) {
   // Calculate the result of the function and return it
+  return num1 * num2;
 }
 
 // Assign the result of calling the function the variable `result`
diff --git a/exercises/K-functions-parameters/exercise2.js b/exercises/K-functions-parameters/exercise2.js
index db7a8904b..0d0c4b3c0 100644
--- a/exercises/K-functions-parameters/exercise2.js
+++ b/exercises/K-functions-parameters/exercise2.js
@@ -1,4 +1,7 @@
 // Declare your function first
+function divide(num1, num2) {
+  return num1 / num2;
+}
 
 var result = divide(3, 4);
 
diff --git a/exercises/K-functions-parameters/exercise3.js b/exercises/K-functions-parameters/exercise3.js
index 537e9f4ec..3341b2910 100644
--- a/exercises/K-functions-parameters/exercise3.js
+++ b/exercises/K-functions-parameters/exercise3.js
@@ -1,4 +1,7 @@
 // Write your function here
+function createGreeting(name) {
+  return "Hello, my name is " + name;
+}
 
 var greeting = createGreeting("Daniel");
 
diff --git a/exercises/K-functions-parameters/exercise4.js b/exercises/K-functions-parameters/exercise4.js
index 7ab44589e..57c2f51b0 100644
--- a/exercises/K-functions-parameters/exercise4.js
+++ b/exercises/K-functions-parameters/exercise4.js
@@ -1,5 +1,7 @@
 // Declare your function first
-
+function addingNumbers(num1, num2) {
+  return num1 + num2;
+}
 // Call the function and assign to a variable `sum`
-
+let sum = addingNumbers(13, 124);
 console.log(sum);
diff --git a/exercises/K-functions-parameters/exercise5.js b/exercises/K-functions-parameters/exercise5.js
index 7c5bcd605..8973b5d54 100644
--- a/exercises/K-functions-parameters/exercise5.js
+++ b/exercises/K-functions-parameters/exercise5.js
@@ -1,4 +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);
 
diff --git a/exercises/L-functions-nested/exercise.js b/exercises/L-functions-nested/exercise.js
index a5d377442..7110f1212 100644
--- a/exercises/L-functions-nested/exercise.js
+++ b/exercises/L-functions-nested/exercise.js
@@ -3,3 +3,19 @@ var mentor2 = "Irina";
 var mentor3 = "Mimi";
 var mentor4 = "Rob";
 var mentor5 = "Yohannes";
+
+function createUppercaseNames(string) {
+  return string.toUpperCase();
+}
+
+function createShoutyGreeting(name) {
+  let mentorName = createUppercaseNames(name);
+  let message = "HELLO " + mentorName;
+  return message;
+}
+
+console.log(createShoutyGreeting(mentor1));
+console.log(createShoutyGreeting(mentor2));
+console.log(createShoutyGreeting(mentor3));
+console.log(createShoutyGreeting(mentor4));
+console.log(createShoutyGreeting(mentor5));
diff --git a/extra/1-currency-conversion.js b/extra/1-currency-conversion.js
index d82e59480..b57907298 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(pound) {
+  return pound * 1.4;
+}
 
 /*
   CURRENCY CONVERSION
@@ -15,7 +17,11 @@ 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(pound) {
+  let percentageToConvert = pound * 0.99;
+  let totalBrazilianAmount = percentageToConvert * 5.7;
+  return parseFloat(totalBrazilianAmount.toFixed(2));
+}
 
 /* ======= TESTS - DO NOT MODIFY ===== 
 There are some Tests in this file that will help you work out if your code is working.
diff --git a/extra/2-piping.js b/extra/2-piping.js
index 9c8ebc76a..77fddb501 100644
--- a/extra/2-piping.js
+++ b/extra/2-piping.js
@@ -16,26 +16,27 @@
   the final result to the variable goodCode
 */
 
-function add() {
-
+function add(num1, num2) {
+  return num1 + num2;
 }
 
-function multiply() {
-
+function multiply(a, b) {
+  return a * b;
 }
 
-function format() {
-
+function format(amount) {
+  return `£${parseFloat(amount.toFixed(1))}`;
 }
 
 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 addedNumbers = add(startingValue, 10);
+let multipliedNumbers = multiply(addedNumbers, 2);
+let goodCode = format(multipliedNumbers);
 
 /* ======= TESTS - DO NOT MODIFY ===== 
 There are some Tests in this file that will help you work out if your code is working.
diff --git a/extra/3-magic-8-ball.js b/extra/3-magic-8-ball.js
index f3adbefa5..9821141e6 100644
--- a/extra/3-magic-8-ball.js
+++ b/extra/3-magic-8-ball.js
@@ -43,11 +43,52 @@
     Very doubtful.
 */
 
+const veryPositive = [
+  "It is certain.",
+  "It is decidedly so.",
+  "Without a doubt.",
+  "Yes - definitely.",
+  "You may rely on it.",
+];
+
+const positive = [
+  "As I see it, yes.",
+  "Most likely.",
+  "Outlook good.",
+  "Yes.",
+  "Signs point to yes.",
+];
+
+const negative = [
+  "Reply hazy, try again.",
+  "Ask again later.",
+  "Better not tell you now.",
+  "Cannot predict now.",
+  "Concentrate and ask again.",
+];
+
+const veryNegative = [
+  "Don't count on it.",
+  "My reply is no.",
+  "My sources say no.",
+  "Outlook not so good.",
+  "Very doubtful.",
+];
+
+const allAnswers = veryPositive.concat(positive, negative, veryNegative);
+
 // This should log "The ball has shaken!"
 // and return the answer.
 function shakeBall() {
   //Write your code in here
+
+  console.log("The ball has shaken!");
+
+  const answerIndex = Math.floor(Math.random() * allAnswers.length);
+
+  return allAnswers[answerIndex];
 }
+let ans = shakeBall();
 
 /* 
   This function should say whether the answer it is given is
@@ -58,9 +99,21 @@ 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
+
+  if (veryPositive.includes(answer)) {
+    return "very positive";
+  } else if (positive.includes(answer)) {
+    return "positive";
+  } else if (negative.includes(answer)) {
+    return "negative";
+  } else if (veryNegative.includes(answer)) {
+    return "very negative";
+  }
 }
+checkAnswer(ans);
 
 /* 
 ==================================
@@ -101,7 +154,9 @@ test("magic 8 ball returns different values each time", () => {
     );
   }
 
-  let seenPositivities = new Set(Array.from(seenAnswers.values()).map(checkAnswer));
+  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"
diff --git a/mandatory/1-syntax-errors.js b/mandatory/1-syntax-errors.js
index a10cc9ac2..98360ac6b 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) {
+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;
 }
 
 /* 
diff --git a/mandatory/2-logic-error.js b/mandatory/2-logic-error.js
index 9cca7603b..37c4ebc15 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;
 }
 
 /* 
diff --git a/mandatory/3-function-output.js b/mandatory/3-function-output.js
index 5a953ba60..0dd2a0a80 100644
--- a/mandatory/3-function-output.js
+++ b/mandatory/3-function-output.js
@@ -1,9 +1,11 @@
 // Add comments to explain what this function does. You're meant to use Google!
+// Whenever this function is called, it generates a random number and multiplies it by 10.
 function getRandomNumber() {
   return Math.random() * 10;
 }
 
 // Add comments to explain what this function does. You're meant to use Google!
+//This function takes two parameters which are strings and concatenates them into one string.
 function combine2Words(word1, word2) {
   return word1.concat(word2);
 }
@@ -11,6 +13,8 @@ function combine2Words(word1, 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.
+  // We could not use concat() because it only accepts strings. It would not meet all conditions of the test.
+  return firstWord + " " + secondWord + " " + thirdWord;
 }
 
 /* 
diff --git a/mandatory/4-tax.js b/mandatory/4-tax.js
index ba77c7ae2..cf7b4798b 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 * 0.2;
+}
 
 /*
   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 totalAmount = calculateSalesTax(price);
+  return `£${totalAmount.toFixed(2)}`;
+}
 
 /* 
 ===================================================
diff --git a/package.json b/package.json
index 58555936d..778df9683 100644
--- a/package.json
+++ b/package.json
@@ -14,7 +14,9 @@
     "url": "https://github.com/CodeYourFuture/JavaScript-Core-1-Coursework-Week1/issues"
   },
   "jest": {
-    "setupFilesAfterEnv": ["jest-extended"]
+    "setupFilesAfterEnv": [
+      "jest-extended"
+    ]
   },
   "homepage": "https://github.com/CodeYourFuture/JavaScript-Core-1-Coursework-Week1#readme",
   "devDependencies": {