JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container">
    <div class="item">
        a
    </div>
    <div class="item">
        b
    </div>
</div>

CSS

#container {    
    border: solid 1px #000;
    display: flex;    
	  flex-direction: row;
	  justify-content: space-between;
    padding: 10px;
    height: 50px;
}

.item {
    width: 20%;
    border: solid 1px #000;
    text-align: center;
}