JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
    <div class="red">Red</div>
    <div class="green">green</div>
    <div class="blue">blue</div>
</div>

CSS

.container{border: 2px solid black; padding: 5px; position: relative; width: 100%; display: flex;}

.container div {height: 20px;}

.red{border: 2px solid red; flex: 1}

.green{border: 2px solid green; flex: 1}

.blue{border: 2px solid blue; flex-shrink: 1; width: 100%}