test.draw.html

<body></body>
<div style="display: flex">

    <div class="flex-child a">
      Flex Column 12
    </div>
    
    <div class="flex-child b">
      Flex Column 2
    </div>
    <div class="flex-child c">
        Flex Column 3ljk
      </div>
    
  </div>

  <style>
    .flex-container {
    display: flex;
}

.flex-child {
    border: 2px solid blue;
}  

.a {
    flex:0.5;
} 
.b {
    flex:0.3;
} 
.c {
    flex:0.01;
} 
  </style>