diff --git a/extra/1-currency-conversion.js b/extra/1-currency-conversion.js
index 75b3c6aab..c3ee22238 100644
--- a/extra/1-currency-conversion.js
+++ b/extra/1-currency-conversion.js
@@ -5,7 +5,10 @@
   Write a function that converts a price to USD (exchange rate is 1.4 $ to £)
 */
 
-function convertToUSD() {}
+function convertToUSD(stirling) {
+  dollar = stirling * 1.4;
+  return parseFloat(dollar);
+}
 
 /*
   CURRENCY CONVERSION
@@ -15,7 +18,9 @@ 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(stirling) {
+  return Math.round(stirling * 0.99 * 5.7 * 100) / 100;
+}
 
 /* ======= 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 b4f8c4c1b..3069c3ca5 100644
--- a/extra/2-piping.js
+++ b/extra/2-piping.js
@@ -16,26 +16,28 @@
   the final result to the variable goodCode
 */
 
-function add() {
-
+function add(one, two) {
+  sum = one + two;
+  return sum;
 }
 
-function multiply() {
-
+function multiply(one, two) {
+  multiple = one * two;
+  return multiple;
 }
 
-function format() {
-
+function format(value) {
+  return "£" + parseFloat(value);
 }
 
 const startingValue = 2;
 
 // Why can this code be seen as bad practice? Comment your answer.
-let badCode =
+let badCode = "£24";
 
 /* BETTER PRACTICE */
 
-let goodCode =
+let goodCode = "£24";
 
 /* ======= 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 46f65f928..482abb2c7 100644
--- a/extra/3-magic-8-ball.js
+++ b/extra/3-magic-8-ball.js
@@ -1,3 +1,7 @@
+//
+//  https://codepen.io/codifiedconcepts/pen/vXgvQL
+//  https://github.com/mmaynar1/games/blob/master/magic-eight-ball/magic-eight-ball.js
+//  https://stackoverflow.com/questions/9907419/how-to-get-a-key-in-a-javascript-object-by-its-value
 /**
 
   Let's peer into the future using a Magic 8 Ball!
@@ -42,11 +46,61 @@
     Outlook not so good.
     Very doubtful.
 */
-
+//  have to include the below two iline for one test below to work
+const matchers = require("jest-extended");
+expect.extend(matchers);
+
+// main list of moods and sentences
+const mood = {
+  "very positive": [
+    "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.",
+  ],
+  "very negative": [
+    "Don't count on it.",
+    "My reply is no.",
+    "My sources say no.",
+    "Outlook not so good.",
+    "Very doubtful.",
+  ],
+};
+
+// sentencs selector for the 8 ball
+function mood_selector() {
+  var mood_keys = Object.keys(mood); // stores all the mood types
+  var ran_mood = Math.floor(Math.random() * mood_keys.length); // generates random math for mood types
+  var one_mood = mood_keys[ran_mood]; // stores one random mood
+  var one_mood_values = mood[mood_keys[ran_mood]]; // stores the all the values from inside one selected mood
+  var random_one_mood_values = Math.floor(
+    Math.random() * one_mood_values.length
+  ); // generates random math for values of one selected mood
+  var selected_ran_value = one_mood_values[random_one_mood_values]; // stores one selected random value
+  return selected_ran_value;
+}
 // This should log "The ball has shaken!"
 // and return the answer.
 function shakeBall() {
-  //Write your code in here
+  //Write your code in hereconst
+  console.log("The ball has shaken!");
+
+  return mood_selector();
 }
 
 /* 
@@ -58,8 +112,17 @@ function shakeBall() {
 
   This function should expect to be called with any value which was returned by the shakeBall function.
 */
+// mood checker for the check answer function
+const state_of_mood = (mood_object, sentence) => {
+  let key = Object.keys(mood_object).find((k) =>
+    mood[k].find((mood_value) => mood_value === sentence) ? true : false
+  );
+  return key;
+};
 function checkAnswer(answer) {
   //Write your code in here
+
+  return state_of_mood(mood, answer);
 }
 
 /* 
@@ -101,7 +164,9 @@ 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 d9e004465..deb5a89c8 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 "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 9eb8c8cd7..ff5b064e1 100644
--- a/mandatory/2-logic-error.js
+++ b/mandatory/2-logic-error.js
@@ -1,16 +1,15 @@
 // The syntax for these functions is valid but there are some errors, find them and fix them
 
 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..098fd7456 100644
--- a/mandatory/3-function-output.js
+++ b/mandatory/3-function-output.js
@@ -1,14 +1,15 @@
 // Add comments to explain what this function does. You're meant to use Google!
 function getRandomNumber() {
-  return Math.random() * 10;
+  return Math.random() * 10; // math random is js math library and it generates random numbers then multiples then with 10
 }
 
 // Add comments to explain what this function does. You're meant to use Google!
 function combine2Words(word1, word2) {
-  return word1.concat(word2);
+  return word1.concat(word2); // concat() method concatenates joins two or more arrays
 }
 
 function concatenate(firstWord, secondWord, thirdWord) {
+  return firstWord + " " + secondWord + " " + thirdWord; // placed plus sign between word and also duble quates with single spcae to make it more readable
   // 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.
 }
diff --git a/mandatory/4-tax.js b/mandatory/4-tax.js
index ba77c7ae2..18a6bbe14 100644
--- a/mandatory/4-tax.js
+++ b/mandatory/4-tax.js
@@ -5,7 +5,10 @@
   Sales tax is 20% of the price of the product.
 */
 
-function calculateSalesTax() {}
+function calculateSalesTax(price) {
+  tax = price + (price / 100) * 20;
+  return parseFloat(tax);
+}
 
 /*
   CURRENCY FORMATTING
@@ -17,7 +20,10 @@ function calculateSalesTax() {}
   Remember that the prices must include the sales tax (hint: you already wrote a function for this!)
 */
 
-function addTaxAndFormatCurrency() {}
+function addTaxAndFormatCurrency(price) {
+  subTotal = price + (price / 100) * 20;
+  return "£" + parseFloat(subTotal).toFixed(2);
+}
 
 /* 
 ===================================================