JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
  <div class="left">
    <div class="blue div">Left</div>
  </div>
  <div class="right">
    <div class="red div">Right top</div>
    <div class="green div"> Right bottom</div>
  </div>
</div>

CSS

.container{
  display: block;
}
.div{
  display: block;
  background:#cccccc;
}
.left{
  float:left;
  width: 70%;
  height: 300px;
}
.left div{
  height:300px;
}
.right{
  float:left;
  width: 30%;
}
.right div{
  height:300px;
}
.red{
  background:#ff0000;
}
.green{
  background:#00ff00;
}
.blue{
  background:#0000ff;
}