diff --git a/Exercises/1-let.js b/Exercises/1-let.js
index d705443..d03476a 100644
--- a/Exercises/1-let.js
+++ b/Exercises/1-let.js
@@ -1,5 +1,5 @@
 'use strict';
 
-let name = undefined;
+let name = 'Sergey';
 
 module.exports = { name };
diff --git a/Exercises/2-const.js b/Exercises/2-const.js
index 5512738..9ea5205 100644
--- a/Exercises/2-const.js
+++ b/Exercises/2-const.js
@@ -1,5 +1,5 @@
 'use strict';
 
-const year = undefined;
+const year = 1991;
 
 module.exports = { year };
diff --git a/Exercises/3-hello.js b/Exercises/3-hello.js
index a597391..96bfb1b 100644
--- a/Exercises/3-hello.js
+++ b/Exercises/3-hello.js
@@ -1,5 +1,7 @@
 'use strict';
 
-const hello = null;
+const hello = name => {
+  console.log(name);
+};
 
 module.exports = { hello };
diff --git a/Exercises/4-range.js b/Exercises/4-range.js
index 31bd852..40c259a 100644
--- a/Exercises/4-range.js
+++ b/Exercises/4-range.js
@@ -1,5 +1,11 @@
 'use strict';
 
-const range = null;
+const range = (start, end) => {
+  const resArr = [];
+  for (let i = start; i <= end; i++) {
+    resArr.push(i);
+  }
+  return resArr;
+};
 
 module.exports = { range };
diff --git a/Exercises/5-range-odd.js b/Exercises/5-range-odd.js
index 54bb5b4..8b8f772 100644
--- a/Exercises/5-range-odd.js
+++ b/Exercises/5-range-odd.js
@@ -1,5 +1,13 @@
 'use strict';
 
-const rangeOdd = null;
+const rangeOdd = (start, end) => {
+  const resArr = [];
+  for (let i = start; i <= end; i++) {
+    if (i % 2 !== 0) {
+      resArr.push(i);
+    }
+  }
+  return resArr;
+};
 
 module.exports = { rangeOdd };
diff --git a/Exercises/6-calculate.js b/Exercises/6-calculate.js
index dfecf6b..af9f4b2 100644
--- a/Exercises/6-calculate.js
+++ b/Exercises/6-calculate.js
@@ -1,11 +1,17 @@
 'use strict';
 
-const square = null;
+const square = x => x * x;
 
-const cube = null;
+const cube = x => x ** 3;
 
-const average = null;
+const average = (a, b) => (a + b) / 2;
 
-const calculate = null;
+const calculate = () => {
+  const resArr = [];
+  for (let i = 0; i <= 9; i++) {
+    resArr.push(average(square(i), cube(i)));
+  }
+  return resArr;
+};
 
 module.exports = { square, cube, average, calculate };
diff --git a/Exercises/7-objects.js b/Exercises/7-objects.js
index 0920026..1503f24 100644
--- a/Exercises/7-objects.js
+++ b/Exercises/7-objects.js
@@ -1,5 +1,15 @@
 'use strict';
 
-const fn = null;
+const fn = () => {
+  const constObj = { name: 'Mira' };
+  let letObj = { name: 'Mira' };
+
+  constObj.name = 'Marco';
+  letObj.name = 'Alex';
+
+  //this assignment won't work because const reference can't be changed.
+  //constObj = {};
+  letObj = {};
+};
 
 module.exports = { fn };
diff --git a/Exercises/8-create.js b/Exercises/8-create.js
index ac27ddd..f400582 100644
--- a/Exercises/8-create.js
+++ b/Exercises/8-create.js
@@ -1,5 +1,5 @@
 'use strict';
 
-const createUser = null;
+const createUser = (name, city) => ({ name, city });
 
 module.exports = { createUser };
diff --git a/Exercises/9-array.js b/Exercises/9-array.js
index 466c69a..a2c4ba8 100644
--- a/Exercises/9-array.js
+++ b/Exercises/9-array.js
@@ -1,7 +1,16 @@
 'use strict';
 
-const phonebook = null;
+const phonebook = [
+  { name: 'Marcus', phone: '+234829304823904' },
+  { name: 'Aurelius', phone: '+234823742' },
+  { name: 'Marcus2', phone: '+092374928734' },
+  { name: 'Marcus3', phone: '+1893167491629' },
+];
 
-const findPhoneByName = null;
+const findPhoneByName = name => {
+  for (const r of phonebook) {
+    if (r.name === name) return r.phone;
+  }
+};
 
 module.exports = { phonebook, findPhoneByName };
diff --git a/Exercises/a-hash.js b/Exercises/a-hash.js
index 466c69a..a32d561 100644
--- a/Exercises/a-hash.js
+++ b/Exercises/a-hash.js
@@ -1,7 +1,12 @@
 'use strict';
 
-const phonebook = null;
+const phonebook = {
+  'Marcus': '+234829304823904',
+  'Aurelius': '+234823742',
+  'Marcus2': '+092374928734',
+  'Marcus3': '+1893167491629',
+};
 
-const findPhoneByName = null;
+const findPhoneByName = name => phonebook[name];
 
 module.exports = { phonebook, findPhoneByName };