JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container">
    <div id="fluid">FLUID</div>
    <div id="fixed">FIXED</div>
</div>

CSS

#container {
    margin: 0 auto;
    overflow: hidden;
    position: relative;
}
#fixed, #fluid {
    padding: 20px 0;
    text-align: center;
}
#fixed {
    background: #eee;
    float: right;
    width: 320px;
}
#fluid {
    background: #ccc;
    left: 0;
    position: absolute;
    right: 320px;
}