JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html>
    <head>
        <title>test2</title>
    </head>
    <body>
        <div id="out">
            <div id="left">left</div>
            <div id="right">right</div>
        </div>
    </body>
</html>

CSS

#out {
    position:relative;
    width:800px;
    height:200px;
    background:#fdd;
    border:1px solid black;
}
#left {
    position:relative;
    height:180px;
    background:#ffd;
    width:100%;
    float:left;
}
#right {
    position:relative;
    width:200px;
    height:180px;
    background:#dfd;
    float:right;
}