diff --git a/bjs/07_Number_and_string/index.html b/bjs/07_Number_and_string/index.html
index 645e1c0f..d4dbe7ff 100644
--- a/bjs/07_Number_and_string/index.html
+++ b/bjs/07_Number_and_string/index.html
@@ -18,14 +18,40 @@
                         <input class="form-control input-window" id="inputWindow" value="">
                         <div class="row no-gutters">
                             <div class="col">
-                                <button class="btn btn-outline-danger form-control" id="btn_clr">C</button>
-                            </div>
-                        </div>
+                                <button class="btn btn-danger form-control" id="btn_clr">C</button>
+                            </div>                 
+                            <div class="row no-gutters">       
+                                <div class="col"> 
+                                    <button class="btn btn-primary form-control" id="btn_1">1</button>
+                                    <button class="btn btn-primary form-control" id="btn_4">4</button>
+                                    <button class="btn btn-primary form-control" id="btn_7">7</button>
+                                    <button class="btn btn-primary form-control" id="btn_calc">=</button>
+                                </div>
+                                <div class="col">
+                                    <button class="btn btn-primary form-control" id="btn_2">2</button>
+                                    <button class="btn btn-primary form-control" id="btn_5">5</button>
+                                    <button class="btn btn-primary form-control" id="btn_8">8</button>
+                                    <button class="btn btn-primary form-control" id="btn_0">0</button> 
+                                </div>
+                                <div class="col">
+                                        <button class="btn btn-primary form-control" id="btn_3">3</button>
+                                        <button class="btn btn-primary form-control" id="btn_6">6</button>
+                                        <button class="btn btn-primary form-control" id="btn_9">9</button>
+                                        <button class="btn btn-primary form-control" id="btn_sqrt">√</button>     
+                                </div>
+                                <div class="col">
+                                    <button class="btn btn-primary form-control" id="btn_sum">+</button>
+                                    <button class="btn btn-primary form-control" id="btn_dif">-</button>
+                                    <button class="btn btn-primary form-control" id="btn_mult">*</button>
+                                    <button class="btn btn-primary form-control" id="btn_div">/</button>     
+                                </div>      
+                            </div>           
+                        </div> 
                     </div>
                 </div>
             </div>
         </div>
-    </div>
+    </div>    
 </div>
 <script src="script.js"></script>
 </body>
diff --git a/bjs/07_Number_and_string/script.js b/bjs/07_Number_and_string/script.js
index 4085abce..27170897 100644
--- a/bjs/07_Number_and_string/script.js
+++ b/bjs/07_Number_and_string/script.js
@@ -3,10 +3,97 @@ let operation = null;
 
 const inputWindow = document.getElementById('inputWindow');
 
-
-document.getElementById('btn_clr').addEventListener('click', function () {
+document.querySelector('#btn_clr').addEventListener('click', function () {
     lastOperand = 0;
     operation = null;
     inputWindow.value = '';
 })
 
+document.querySelector('#btn_1').addEventListener('click', function () {
+    inputWindow.value += '1';
+})
+document.querySelector('#btn_2').addEventListener('click', function () {
+    inputWindow.value += '2';
+})
+document.querySelector('#btn_3').addEventListener('click', function () {
+    inputWindow.value += '3';
+})
+document.querySelector('#btn_4').addEventListener('click', function () {
+    inputWindow.value += '4';
+})
+document.querySelector('#btn_5').addEventListener('click', function () {
+    inputWindow.value += '5';
+})
+document.querySelector('#btn_6').addEventListener('click', function () {
+    inputWindow.value += '6';
+})
+document.querySelector('#btn_7').addEventListener('click', function () {
+    inputWindow.value += '7';
+})
+document.querySelector('#btn_8').addEventListener('click', function () {
+    inputWindow.value += '8';
+})
+document.querySelector('#btn_9').addEventListener('click', function () {
+    inputWindow.value += '9';
+})
+document.querySelector('#btn_0').addEventListener('click', function () {
+    inputWindow.value += '0';
+})
+document.querySelector('#btn_sum').addEventListener('click', function () {
+    lastOperand = parseInt(inputWindow.value);
+    operation = 'sum';
+    inputWindow.value = '';
+})
+document.querySelector('#btn_dif').addEventListener('click', function () {
+    lastOperand = parseInt(inputWindow.value);
+    operation = 'dif';
+    inputWindow.value = '';
+})
+document.querySelector('#btn_mult').addEventListener('click', function () {
+    lastOperand = parseInt(inputWindow.value);
+    operation = 'mult';
+    inputWindow.value = '';
+})
+document.querySelector('#btn_div').addEventListener('click', function () {
+    lastOperand = parseInt(inputWindow.value);
+    operation = 'div';
+    inputWindow.value = '';
+})
+document.querySelector('#btn_sqrt').addEventListener('click', function () {
+    lastOperand = parseInt(inputWindow.value);
+    operation = 'sqrt';
+    inputWindow.value = '';
+})
+
+document.querySelector('#btn_calc').addEventListener('click', function () {
+   if (operation === 'sum'){
+        const result = lastOperand + parseInt(inputWindow.value);
+        operation = null;
+        lastOperand = 0;
+        inputWindow.value = result;
+   }
+   if (operation === 'dif'){
+        const result = lastOperand - parseInt(inputWindow.value);
+        operation = null;
+        lastOperand = 0;
+        inputWindow.value = result;
+    }
+    if (operation === 'mult'){
+        const result = lastOperand * parseInt(inputWindow.value);
+        operation = null;
+        lastOperand = 0;
+        inputWindow.value = result;
+        }
+    if (operation === 'div'){
+        const result = lastOperand / parseInt(inputWindow.value);
+        operation = null;
+        lastOperand = 0;
+        inputWindow.value = result;
+        }
+    if (operation === 'sqrt'){
+        const result = Math.sqrt(lastOperand);
+        operation = null;
+        lastOperand = 0;
+        inputWindow.value = result;
+        }
+})
\ No newline at end of file
diff --git a/bjs/07_Number_and_string/style.css b/bjs/07_Number_and_string/style.css
index 5257d402..54434020 100644
--- a/bjs/07_Number_and_string/style.css
+++ b/bjs/07_Number_and_string/style.css
@@ -7,3 +7,9 @@
     text-align: end;
     font-size: x-large;
 }
+.btn { 
+    border: 1px solid transparent; }
+.card-body {
+    background-color: black;
+}
+