diff --git a/.eslintrc.json b/.eslintrc.json
index 188baf7..9b0f412 100644
--- a/.eslintrc.json
+++ b/.eslintrc.json
@@ -18,7 +18,7 @@
     ],
     "linebreak-style": [
       "error",
-      "unix"
+      "windows"
     ],
     "quotes": [
       "error",
@@ -265,4 +265,4 @@
       "never"
     ]
   }
-}
+}
\ No newline at end of file
diff --git a/Exercises/1-for.js b/Exercises/1-for.js
index 62e6ab8..10b9a08 100644
--- a/Exercises/1-for.js
+++ b/Exercises/1-for.js
@@ -1,9 +1,14 @@
 'use strict';
 
 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..e540ee7 100644
--- a/Exercises/2-for-of.js
+++ b/Exercises/2-for-of.js
@@ -1,9 +1,13 @@
 'use strict';
 
 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 val of args) {
+    result += val;
+  }
+
+  return result;
 };
 
 module.exports = { sum };
diff --git a/Exercises/3-while.js b/Exercises/3-while.js
index 6110b9f..9297038 100644
--- a/Exercises/3-while.js
+++ b/Exercises/3-while.js
@@ -1,9 +1,14 @@
 'use strict';
 
 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 i = 0;
+  let res = 0;
+
+  while (i < args.length) {
+    res += args[i++];
+  }
+
+  return res;
 };
 
 module.exports = { sum };
diff --git a/Exercises/4-do-while.js b/Exercises/4-do-while.js
index 22d4464..16c331a 100644
--- a/Exercises/4-do-while.js
+++ b/Exercises/4-do-while.js
@@ -1,9 +1,16 @@
 'use strict';
 
 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) return 0;
+  let i = 0;
+  let res = 0;
+
+  do {
+    res += args[i++];
+  } while (i < args.length);
+
+  return res;
 };
 
+
 module.exports = { sum };
diff --git a/Exercises/5-reduce.js b/Exercises/5-reduce.js
index a9cb44c..d173537 100644
--- a/Exercises/5-reduce.js
+++ b/Exercises/5-reduce.js
@@ -1,8 +1,6 @@
 '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, val) => acc += val, 0);
+
 
 module.exports = { sum };
diff --git a/Exercises/6-matrix.js b/Exercises/6-matrix.js
index b768c0a..f94b2f7 100644
--- a/Exercises/6-matrix.js
+++ b/Exercises/6-matrix.js
@@ -1,9 +1,16 @@
 'use strict';
 
 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
+  const arrOfNum = [];
+
+  for (let i = 0; i < matrix.length; i++) {
+    const row = matrix[i];
+    for (let j = 0; j < row.length; j++) {
+      arrOfNum.push(Math.max.apply(null, row));
+    }
+  }
+
+  return Math.max.apply(null, arrOfNum);
 };
 
 module.exports = { max };
diff --git a/Exercises/7-ages.js b/Exercises/7-ages.js
index fc8089b..63d185c 100644
--- a/Exercises/7-ages.js
+++ b/Exercises/7-ages.js
@@ -1,19 +1,14 @@
 'use strict';
 
 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 personAge = {};
+
+  for (const person in persons) {
+    const { died, born } = persons[person];
+    personAge[person] = died - born;
+  }
+
+  return personAge;
 };
 
 module.exports = { ages };
diff --git a/package.json b/package.json
index c545366..4ef755a 100644
--- a/package.json
+++ b/package.json
@@ -11,4 +11,4 @@
     "eslint": "^7.17.0",
     "hpw": "^0.1.14"
   }
-}
+}
\ No newline at end of file