W3Schools Tryit Editor

<!DOCTYPE html>
<html>
<head>
<style> 
#myDIV {
  width: 220px;
  height: 300px;
  border: 1px solid black;
  display: flex;
}
</style>
</head>
<body>

<p>Click the "Try it" button to set the flex property of ALL DIV elements inside the "myDIV" element:</p>

<div id="myDIV">
  <div style="background-color:coral;">RED</div>
  <div style="background-color:lightblue;">BLUE</div>  
  <div style="background-color:lightgreen;">Green div with more content.</div>
</div>

<p><b>Note:</b> IE11 and Edge support the flex property. IE 10 supports an alternative, the msFlex property.</p>

</body>

</html>