diff --git a/javascript-basics-04-tdd/questions.js b/javascript-basics-04-tdd/questions.js
index d56a923..4d1226d 100644
--- a/javascript-basics-04-tdd/questions.js
+++ b/javascript-basics-04-tdd/questions.js
@@ -1,101 +1,110 @@
 
 const stringSize = (text) => {
-
-}
+    return text.length;
+};
 const replaceCharacterE = (text) => {
-
-}
+    return text.replace("e", " ");
+};
 const concatString = (text1, text2) => {
-
-}
+    return (text1 + text2);
+};
 const showChar5 = (text) => {
-
-}
+    return (text.charAt(4));
+};
 const showChar9 = (text) => {
-
-}
+    return text.slice(0, 9);
+};
 const toCapitals = (text) => {
-
-}
+    return text.toUpperCase();
+};
 const toLowerCase = (text) => {
-
-}
+    return text.toLowerCase();
+};
 const removeSpaces = (text) => {
-
-}
+    return text.trim();
+};
 const IsString = (text) => {
-
-}
+    return typeof text === "string";
+};
 
 const getExtension = (text) => {
-
-}
+    return text.split(".").pop();
+};
 const countSpaces = (text) => {
-
-}
+    return text.split(" ").length - 1;
+};
 const InverseString = (text) => {
-
-}
+    return text.split("").reverse().join("");
+};
 
 const power = (x, y) => {
-
-}
+    return Math.pow(x, y);
+};
 const absoluteValue = (num) => {
-
-}
+    return Math.abs(num);
+};
 const absoluteValueArray = (array) => {
-
-}
+    return array.map((value) => Math.abs(value));
+};
 const circleSurface = (radius) => {
-
-}
+    return Math.round(Math.PI * radius * radius);
+};
 const hypothenuse = (ab, ac) => {
-
-}
+    return Math.sqrt(ab * ab + ac * ac);
+};
 const BMI = (weight, height) => {
-
-}
+    return parseFloat((weight / (height * height)).toFixed(2));
+};
 
 const createLanguagesArray = () => {
-
-}
+    const languages = ["Html", "CSS", "Java", "PHP"];
+    return languages;
+};
 
 const createNumbersArray = () => {
-
-}
+    const numbers = [0, 1, 2, 3, 4, 5];
+    return numbers;
+};
 
 const replaceElement = (languages) => {
-
-}
+    languages[2] = "Javascript";
+    return languages;
+};
 
 const addElement = (languages) => {
-
-}
+    languages.push("Ruby", "Python");
+    return languages;
+};
 
 const addNumberElement = (numbers) => {
-
-}
+    numbers.unshift(-2, -1);
+    return numbers;
+};
 
 const removeFirst = (languages) => {
-
-}
+    languages.shift();
+    return languages;
+};
 
 const removeLast = (languages) => {
-
-}
+    languages.pop();
+    return languages;
+};
 
 const convertStrToArr = (social_arr) => {
-
-}
+    const strToaArr = social_arr.split(",");
+    return strToaArr;
+};
 
 const convertArrToStr = (languages) => {
-
-}
+    const arrToStr = languages.join();
+    return arrToStr;
+};
 
 const sortArr = (social_arr) => {
-
-}
+    return social_arr.sort();
+};
 
 const invertArr = (social_arr) => {
-
-}
\ No newline at end of file
+    return social_arr.reverse();
+};
\ No newline at end of file