diff --git a/src/carbon-dating.js b/src/carbon-dating.js
index 8b53e0136e..6c3f2d8906 100644
--- a/src/carbon-dating.js
+++ b/src/carbon-dating.js
@@ -17,9 +17,13 @@ const HALF_LIFE_PERIOD = 5730;
  * dateSample('WOOT!') => false
  *
  */
-function dateSample(/* sampleActivity */) {
-  // Remove line below and write your code here
-  throw new NotImplementedError('Not implemented');
+function dateSample( sampleActivity ) {
+  if (typeof sampleActivity !== 'string' || sampleActivity === '' || !Number(sampleActivity) || Number(sampleActivity) <= 0 || Number(sampleActivity) > 15){
+    return false;
+  }
+  const k = Math.LN2 / HALF_LIFE_PERIOD;
+  const age = Math.log(MODERN_ACTIVITY / Number(sampleActivity)) / k;
+  return Math.ceil(age);
 }
 
 module.exports = {
diff --git a/src/common-character-count.js b/src/common-character-count.js
index 681b1f6656..1df36013d8 100644
--- a/src/common-character-count.js
+++ b/src/common-character-count.js
@@ -11,10 +11,16 @@ const { NotImplementedError } = require('../lib');
  * For s1 = "aabcc" and s2 = "adcaa", the output should be 3
  * Strings have 3 common characters - 2 "a"s and 1 "c".
  */
-
-function getCommonCharacterCount(/* s1, s2 */) {
-  // Remove line below and write your code here
-  throw new NotImplementedError('Not implemented');
+function getCommonCharacterCount( s1, s2 ) {
+  return s1.split('').reduce((prev, value, i) => {
+    let index = s2.indexOf(value);
+    if ( index !== -1 ){
+      prev += 1;
+      s2 = s2.replace(s2[index], '');
+      return prev;
+    }
+    return prev;
+  },0)
 }
 
 module.exports = {
diff --git a/src/count-cats.js b/src/count-cats.js
index e178c79f6c..e208199813 100644
--- a/src/count-cats.js
+++ b/src/count-cats.js
@@ -14,9 +14,16 @@ const { NotImplementedError } = require('../lib');
  * ]) => 3`
  *
  */
-function countCats(/* matrix */) {
-  // Remove line below and write your code here
-  throw new NotImplementedError('Not implemented');
+function countCats( matrix ) {
+  let count = 0;
+  for (let i = 0; i < matrix.length; i++) {
+    for (let j = 0; j < matrix[i].length; j++) {
+      if (matrix[i][j] === "^^"){
+        count += 1;
+      }
+    }
+  }
+  return count;
 }
 
 module.exports = {
diff --git a/src/delete-digit.js b/src/delete-digit.js
index c4f3a2d212..b685ea7007 100644
--- a/src/delete-digit.js
+++ b/src/delete-digit.js
@@ -11,9 +11,14 @@ const { NotImplementedError } = require('../lib');
  * For n = 152, the output should be 52
  *
  */
-function deleteDigit(/* n */) {
-  // Remove line below and write your code here
-  throw new NotImplementedError('Not implemented');
+function deleteDigit( n ) {
+  let str = n.toString();
+  let arrSumm = [];
+  for (let i = 0; i < str.length; i++) {
+    let newSumm = Number(str.replace(str[i], ''));
+    arrSumm.push(newSumm);
+  }
+  return Math.max(...arrSumm)
 }
 
 module.exports = {
diff --git a/src/dns-stats.js b/src/dns-stats.js
index 4c1d845c43..37eb491dbd 100644
--- a/src/dns-stats.js
+++ b/src/dns-stats.js
@@ -22,9 +22,23 @@ const { NotImplementedError } = require('../lib');
  * }
  *
  */
-function getDNSStats(/* domains */) {
-  // Remove line below and write your code here
-  throw new NotImplementedError('Not implemented');
+function getDNSStats( domains ) {
+  const objDNS = {};
+  for (let i = 0; i < domains.length; i++) {
+    let reverseArr = domains[i].split('.').reverse();
+    let dns = '';
+    for (let j = 0; j < reverseArr.length; j++) {
+      dns += `.${reverseArr[j]}`;
+      if(objDNS[dns]){
+        objDNS[dns]++;
+      }
+      else{
+        objDNS[dns] = 1;
+      }
+    }
+    
+  }
+  return objDNS;
 }
 
 module.exports = {
diff --git a/src/dream-team.js b/src/dream-team.js
index ca4b688b5d..edfd14e560 100644
--- a/src/dream-team.js
+++ b/src/dream-team.js
@@ -13,9 +13,18 @@ const { NotImplementedError } = require('../lib');
  * createDreamTeam(['Olivia', 1111, 'Lily', 'Oscar', true, null]) => 'LOO'
  *
  */
-function createDreamTeam(/* members */) {
-  // Remove line below and write your code here
-  throw new NotImplementedError('Not implemented');
+function createDreamTeam( members ) {
+  if(!Array.isArray(members)){
+    return false;
+  }
+
+  return members.reduce((prev, value) => {
+    if(typeof value === 'string'){
+      prev.push(value.trim().at(0).toUpperCase());
+      return prev;
+    }
+    return prev;
+  }, []).sort().join('');
 }
 
 module.exports = {
diff --git a/src/encode-line.js b/src/encode-line.js
index c77a2954dc..00f2be2a03 100644
--- a/src/encode-line.js
+++ b/src/encode-line.js
@@ -1,3 +1,4 @@
+// const { NotImplementedError } = require("../extensions/index.js");
 const { NotImplementedError } = require('../lib');
 
 /**
@@ -10,12 +11,25 @@ const { NotImplementedError } = require('../lib');
  * For aabbbc should return 2a3bc
  *
  */
+function encodeLine(str) {
+  if(str.length === 0) return '';
+  let result = "";
+  let currentChar = str[0];
+  let count = 1;
 
-function encodeLine(/* str */) {
-  // Remove line below and write your code here
-  throw new NotImplementedError('Not implemented');
+  for (let index = 1; index < str.length; index++) {
+    if (currentChar === str[index]) {
+      count++;
+    } else {
+      result += (count > 1 ? count : "") + currentChar;
+      currentChar = str[index];
+      count = 1;
+    }
+  }
+  result += (count > 1 ? count : "") + currentChar;
+  return String(result);
 }
 
 module.exports = {
-  encodeLine
+  encodeLine,
 };
diff --git a/src/get-email-domain.js b/src/get-email-domain.js
index 0fb58b1273..f2031a71bb 100644
--- a/src/get-email-domain.js
+++ b/src/get-email-domain.js
@@ -10,8 +10,9 @@ const { NotImplementedError } = require('../lib');
  * For the input 'prettyandsimple@example.com', the output should be 'example.com'
  *
  */
-function getEmailDomain(/* email */) {
-  throw new NotImplementedError('Not implemented');
+function getEmailDomain( email ) {
+  const index = email.lastIndexOf('@');
+  return email.slice(index +1 );
 }
 
 module.exports = {
diff --git a/src/hanoi-tower.js b/src/hanoi-tower.js
index 9df72f988e..49b7db9a74 100644
--- a/src/hanoi-tower.js
+++ b/src/hanoi-tower.js
@@ -14,9 +14,10 @@ const { NotImplementedError } = require('../lib');
  * calculateHanoi(9, 4308) => { turns: 511, seconds: 427 }
  *
  */
-function calculateHanoi(/* disksNumber, turnsSpeed */) {
-  // Remove line below and write your code here
-  throw new NotImplementedError('Not implemented');
+function calculateHanoi( disksNumber, turnsSpeed ) {
+  const turns = Math.pow(2, disksNumber) - 1;
+  const seconds = Math.floor(turns / turnsSpeed * 3600);
+  return { turns, seconds };
 }
 
 module.exports = {
diff --git a/src/matrix-elements-sum.js b/src/matrix-elements-sum.js
index 813b771fa8..690b5a9244 100644
--- a/src/matrix-elements-sum.js
+++ b/src/matrix-elements-sum.js
@@ -16,9 +16,18 @@ const { NotImplementedError } = require('../lib');
  *
  * The result should be 9
  */
-function getMatrixElementsSum(/* matrix */) {
-  // Remove line below and write your code here
-  throw new NotImplementedError('Not implemented');
+function getMatrixElementsSum( matrix ) {
+  let sum = 0;
+
+  for (let i = 0; i < matrix.length; i++) {
+    for (let j = 0; j < matrix[0].length; j++) {
+      if (i === 0 || matrix[i - 1][j] !== 0) {
+        sum += matrix[i][j];
+      }
+    }
+  }
+
+  return sum;
 }
 
 module.exports = {
diff --git a/src/sum-digits.js b/src/sum-digits.js
index ac605aff3d..df3d21c1b9 100644
--- a/src/sum-digits.js
+++ b/src/sum-digits.js
@@ -12,9 +12,19 @@ const { NotImplementedError } = require('../lib');
  * For 91, the result should be 1 (9 + 1 = 10, 1 + 0 = 1)
  *
  */
-function getSumOfDigits(/* n */) {
-  // Remove line below and write your code here
-  throw new NotImplementedError('Not implemented');
+function getSumOfDigits( n ) {
+  let str = n.toString();
+  let sum = 0;
+
+  for (let i = 0; i < str.length; i++) {
+    sum += parseInt(str[i]);
+  }
+
+  if (sum <= 9) {
+    return sum;
+  }
+
+  return getSumOfDigits(sum);
 }
 
 module.exports = {