JSFiddle - React, Tailwind, and code Playground

HTML

<div id="big">
    <button id="left"><</button>
    <button id="right">></button>
    <div id="center">займи оставшуюся ширину!</div>
</div>

CSS

#big{
        height: 100px;
        background-color: #4bb1cf;        
        width: 100%;
    }
    #left{
        width: 20px;
        height: 100%;        
        display: block;
        float:left;
    }
    #right{
        height: 100%;
        width: 20px;        
        display: block;        
        float:right;
    }
    #center{
        margin:0 20px;
        height: 100%;
        background-color: red;
        display: block;          
    }