JSFiddle - React, Tailwind, and code Playground

HTML

<div class="wrap">
    <div class="a">
        <p>A</p>
    </div>
    <div class="b">
        <p>B</p>
    </div>
</div>

CSS

.wrap {
    margin: 0 0 20px;
    padding: 20px;
    background: #FFA;
    overflow: auto;
    height: 100%;
}
p {
    background: rgba(0, 255, 255, 0.25);
}
.a, .b {
    height: 150px;
}
.a {
    background: rgba(255, 0, 0, 0.25);
    width: 150px;
    float: left;
}
.b {
    background: rgba(0, 0, 255, 0.25);
    margin: 0 0 0 170px;
}