JSFiddle - React, Tailwind, and code Playground

HTML

<div class="block">
    <div class="content"></div>
    <div class="sidebar"></div>
</div>

CSS

.block {
    width: 500px;
}
.content,
.sidebar {
    display: inline-block;
    height:200px;
}
.content {
    width: 350px;
    background-color: blue;
}
.sidebar {
    width: 150px;
    background-color: red;
}