JSFiddle - React, Tailwind, and code Playground

HTML

<div id="menu"></div>
<div id="conteudo2"></div>

CSS

#conteudo2 {
width: -webkit-calc(100% - 150px);
width: -moz-calc(100% - 150px);
width: calc(100% - 150px);
background-color: #333333;
float: left;
height: 920px;
margin-top: -10px;
}

#menu {
width: 150px;
float: left;
height: 900px;
background-color: #f2f2f2;
}