diff --git a/extra/1-currency-conversion.js b/extra/1-currency-conversion.js
index 75b3c6aab..47926a434 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(amount) {
+  return amount * 1.4; 
+}
 
 /*
   CURRENCY CONVERSION
@@ -15,7 +17,18 @@ 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(amount) {
+  let priceFee = amount * 0.99;
+  let convertedPrice = priceFee * 5.7;
+  return Math.round(convertedPrice * 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..e525e5469 100644
--- a/extra/2-piping.js
+++ b/extra/2-piping.js
@@ -16,26 +16,33 @@
   the final result to the variable goodCode
 */
 
-function add() {
-
+function add(num1, num2) {
+  return num1 + num2;
 }
 
-function multiply() {
+function multiply(num1, num2) {
+  return num1 * num2;
 
 }
 
-function format() {
+function format(num1) {
+  return `£${num1}`
 
 }
 
 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 addNumbers = add(startingValue, 10);
+let multiplyAddNumbers = multiply(addNumbers, 2)
+let goodCode = format(multiplyAddNumbers);
 
 /* ======= 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..00807f951 100644
--- a/extra/3-magic-8-ball.js
+++ b/extra/3-magic-8-ball.js
@@ -1,3 +1,5 @@
+const { toBeOneOf } = require('jest-extended');
+
 /**
 
   Let's peer into the future using a Magic 8 Ball!
@@ -45,23 +47,71 @@
 
 // This should log "The ball has shaken!"
 // and return the answer.
+
+
+let randomOneOfVeryPositive = [
+    "It is certain.",
+    "It is decidedly so.",
+    "Without a doubt.",
+    "Yes - definitely.",
+    "You may rely on it."
+];
+
+let randomOneOfPositive = [
+    "As I see it, yes.",
+    "Most likely.",
+    "Outlook good.",
+    "Yes.",
+    "Signs point to yes."
+];
+
+let randomOneOfNegative = [
+    "Reply hazy, try again.",
+    "Ask again later.",
+    "Better not tell you now.",
+    "Cannot predict now.",
+    "Concentrate and ask again."
+];
+
+let randomOneOfVeryNegative = [
+    "Don't count on it.",
+    "My reply is no.",
+    "My sources say no.",
+    "Outlook not so good.",
+    "Very doubtful."
+];
+
+let answersArray = [
+  ...randomOneOfVeryPositive, 
+  ...randomOneOfPositive, 
+  ...randomOneOfNegative, 
+  ...randomOneOfVeryNegative
+];
+
+
 function shakeBall() {
-  //Write your code in here
+  console.log("The ball has shaken!");
+  let randomAnswerIndex = Math.floor(Math.random() * answersArray.length);
+   return answersArray [randomAnswerIndex]
+  
 }
 
-/* 
-  This function should say whether the answer it is given is
-    - very positive
-    - positive
-    - negative
-    - very negative
 
-  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 (randomOneOfVeryPositive.includes(answer)) {
+      return "very positive";
+    } 
+    else if(randomOneOfPositive.includes(answer)) {
+    return "positive";
+   }
+   else if(randomOneOfNegative.includes(answer)) {
+    return "negative";
+   } else if(randomOneOfVeryNegative.includes(answer)) {
+    return "very negative";
+}  
 }
 
+
 /* 
 ==================================
 ======= TESTS - DO NOT MODIFY =====
diff --git a/mandatory/1-syntax-errors.js b/mandatory/1-syntax-errors.js
index d9e004465..6e5c7e0cf 100644
--- a/mandatory/1-syntax-errors.js
+++ b/mandatory/1-syntax-errors.js
@@ -1,16 +1,16 @@
 // 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;
-
-  return "The total is total";
+  total = a + b;
+  return `The total is ${total}`;
 }
 
 /* 
diff --git a/mandatory/2-logic-error.js b/mandatory/2-logic-error.js
index 9eb8c8cd7..694f9cf63 100644
--- a/mandatory/2-logic-error.js
+++ b/mandatory/2-logic-error.js
@@ -1,16 +1,17 @@
 // 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..14bf1c5fb 100644
--- a/mandatory/3-function-output.js
+++ b/mandatory/3-function-output.js
@@ -2,13 +2,17 @@
 function getRandomNumber() {
   return Math.random() * 10;
 }
+//Create a random integer number with digit number which was given by the caller. 
+//Return a random number between 0 and 10:
 
 // Add comments to explain what this function does. You're meant to use Google!
 function combine2Words(word1, word2) {
   return word1.concat(word2);
 }
+//The concat() method is used to merge two or more arrays. This method does not change the existing arrays, but instead returns a new array.
 
 function concatenate(firstWord, secondWord, thirdWord) {
+  return 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.
 }
diff --git a/mandatory/4-tax.js b/mandatory/4-tax.js
index ba77c7ae2..07ad0e39e 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 * 1.2;
+}
 
 /*
   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 priceWithTax = calculateSalesTax(price);
+  return '£' + priceWithTax.toFixed(2);
+}
 
 /* 
 ===================================================