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<!DOCTYPE html>
<html>
<head>
<style>
body {
  background-color:#E7E9EB;
}
#myDIV {
  height:300px;
  background-color:#FFFFFF;
}
#mymain {
  width: 100%;
  height: 100px;
  display: flex;
}
#mymain div {
  padding:5px;
}
#bluediv {
  flex: 0 1 150px;
}
</style>
</head>
<body>
<h1>The flex property</h1>
<div id="myDIV">
<p>Set the flex property of the BLUE div:</p>
<div id="mymain">
  <div style="background-color:coral;">red div</div>
  <div id="bluediv" style="background-color:lightblue;">blue div</div>
  <div style="background-color:khaki;">yellow div</div>
  <div style="background-color:pink;">pink div</div>
</div>
</div>
</body>
</html>