JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container">
    <div id="left">
        left
    </div>
    <div id="right">
        right
    </div>
</div>

CSS

#container
{
  height:40px;
}
#left {
    float:left;
    width:180px;
    background-color:#ff0000;
    height:100%;
}
#right {
    width: 100%;
    background-color:#00FF00;
    height:100%;
}