JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container">
	    	<div id="center"> <h1>center</h1> </div>
	        <div id="right"> <h1>right</h1> </div>
        </div>

CSS

#center{
	background-color: green;
    float: left;
    width: -moz-calc(100% - 200px);
    width: -webkit-calc(100% - 200px);
    width: calc(100% - 200px);
}

#right{
	    background-color: red;
        float: right;
        width: 200px;
}