how to put div side by side using flexbox code example

Example 1: div side by side flex

.float-container {
    border: 3px solid #fff;
    padding: 20px;
}

.float-child {
    width: 50%;
    float: left;
    padding: 20px;
    border: 2px solid red;
}
<div class="float-container">

  <div class="float-child">
    <div class="green">Float Column 1</div>
  </div>
  
  <div class="float-child">
    <div class="blue">Float Column 2</div>
  </div>
  
</div>

Example 2: display two divs side by side flexbox

.float-container {
    border: 3px solid #fff;
    padding: 20px;
}

.float-child {
    width: 50%;
    float: left;
    padding: 20px;
    border: 2px solid red;
}