JSFiddle - React, Tailwind, and code Playground

HTML

<div id="content">
    <div class="box">1</div>
    <div class="box">2</div>
    <div class="box">3</div>
</div>

CSS

#content { display: flex; }
#content > div:nth-child(2) { flex: 1; }

/* can ignore styles below; decorative only */

#content {
    background-color: yellow;
    border: 1px solid #ccc;
}

.box {
    height: 50px;
    width: 75px;
    margin: 5px;
    background-color: lightgreen;
    border: 1px solid #ccc;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1.2em;
}