diff --git a/Exercises/1-for.js b/Exercises/1-for.js
index 62e6ab8..420d433 100644
--- a/Exercises/1-for.js
+++ b/Exercises/1-for.js
@@ -1,9 +1,15 @@
 'use strict';
 
+// Use for loop and accumulator variable
+// to calculate sum of all given arguments
+// For example sum(1, 2, 3) should return 6
+
 const sum = (...args) => {
-  // Use for loop and accumulator variable
-  // to calculate sum of all given arguments
-  // For example sum(1, 2, 3) should return 6
+  let result = 0;
+  for (let i = 0; i < args.length; i++) {
+    result += args[i];
+  }
+  return result;
 };
 
 module.exports = { sum };
diff --git a/Exercises/2-for-of.js b/Exercises/2-for-of.js
index 9965f25..d8dd95b 100644
--- a/Exercises/2-for-of.js
+++ b/Exercises/2-for-of.js
@@ -1,9 +1,15 @@
 'use strict';
 
+// Use for..of loop and accumulator variable
+// to calculate sum of all given arguments
+// For example sum(1, 2, 3) should return 6
+
 const sum = (...args) => {
-  // Use for..of loop and accumulator variable
-  // to calculate sum of all given arguments
-  // For example sum(1, 2, 3) should return 6
+  let result = 0;
+  for (const item of args) {
+    result += item;
+  }
+  return result;
 };
 
 module.exports = { sum };
diff --git a/Exercises/3-while.js b/Exercises/3-while.js
index 6110b9f..21ed3e1 100644
--- a/Exercises/3-while.js
+++ b/Exercises/3-while.js
@@ -1,9 +1,17 @@
 'use strict';
 
+// Use while loop and accumulator variable
+// to calculate sum of all given arguments
+// For example sum(1, 2, 3) should return 6
+
 const sum = (...args) => {
-  // Use while loop and accumulator variable
-  // to calculate sum of all given arguments
-  // For example sum(1, 2, 3) should return 6
+  let result = 0;
+
+  while (args.length > 0) {
+    result += args.pop();
+  }
+
+  return result;
 };
 
 module.exports = { sum };
diff --git a/Exercises/4-do-while.js b/Exercises/4-do-while.js
index 22d4464..4e0e87f 100644
--- a/Exercises/4-do-while.js
+++ b/Exercises/4-do-while.js
@@ -1,9 +1,18 @@
 'use strict';
 
+// Use do..while loop and accumulator variable
+// to calculate sum of all given arguments
+// For example sum(1, 2, 3) should return 6
+
 const sum = (...args) => {
-  // Use do..while loop and accumulator variable
-  // to calculate sum of all given arguments
-  // For example sum(1, 2, 3) should return 6
+  if (args.length === 0) return 0;
+  let result = 0;
+
+  do {
+    result += args.pop();
+  } while (args.length > 0);
+
+  return result;
 };
 
 module.exports = { sum };
diff --git a/Exercises/5-reduce.js b/Exercises/5-reduce.js
index a9cb44c..820bd75 100644
--- a/Exercises/5-reduce.js
+++ b/Exercises/5-reduce.js
@@ -1,8 +1,9 @@
 'use strict';
 
-const sum = (...args) => 0;
 // Use Array.prototype.reduce method
 // to calculate sum of all given arguments
 // For example sum(1, 2, 3) should return 6
 
+const sum = (...args) => args.reduce((acc, value) => acc + value, 0);
+
 module.exports = { sum };
diff --git a/Exercises/6-matrix.js b/Exercises/6-matrix.js
index 0bc42c8..63d56d5 100644
--- a/Exercises/6-matrix.js
+++ b/Exercises/6-matrix.js
@@ -1,9 +1,22 @@
 'use strict';
 
+// Use nested for loop to find max value in 2d matrix
+// For example max([[1, 2, 3], [4, 5, 6], [7, 8, 9]])
+// should return 9
+
+const MAX = (a, b) => (a > b ? a : b);
+
 const max = (matrix) => {
-  // Use nested for loop to find max value in 2d matrix
-  // For example max([[1, 2, 3], [4, 5, 6], [7, 8, 9]])
-  // should return 9
+  // Lorem ipsum dolor sit amet, consectetur adipiscing elit.
+  let maxValue = matrix[0][0];
+
+  for (const row of matrix) {
+    for (const item of row) {
+      maxValue = MAX(item, maxValue);
+    }
+  }
+
+  return maxValue;
 };
 
 module.exports = { max };
diff --git a/Exercises/7-ages.js b/Exercises/7-ages.js
index e90caa2..9bccee6 100644
--- a/Exercises/7-ages.js
+++ b/Exercises/7-ages.js
@@ -1,19 +1,30 @@
 'use strict';
 
+
+// Use for..in to calculate age for each person
+// For example ages({
+//   lenin: { born: 1870, died: 1924 },
+//   mao: { born: 1893, died: 1976 },
+//   gandhi: { born: 1869, died: 1948 },
+//   hirohito: { born: 1901, died: 1989 },
+// })
+
+// should return {
+//   lenin: 54,
+//   mao: 83,
+//   gandhi: 79,
+//   hirohito: 88,
+// }
+
 const ages = (persons) => {
-  // Use for..in to calculate age for each person
-  // For example ages({
-  //   lenin: { born: 1870, died: 1924 },
-  //   mao: { born: 1893, died: 1976 },
-  //   gandhi: { born: 1869, died: 1948 },
-  //   hirohito: { born: 1901, died: 1989 },
-  // })
-  // should return {
-  //   lenin: 54,
-  //   mao: 83,
-  //   gandhi: 79,
-  //   hirohito: 88,
-  // }
+  const result = {};
+
+  for (const name in persons) {
+    const person = persons[name];
+    result[name] = person.died - person.born;
+  }
+
+  return result;
 };
 
 module.exports = { ages };