JSFiddle - React, Tailwind, and code Playground

HTML

<div class="main">
    <div class="left_wrap">
        Hello
    </div>
    <div class="right_wrap">
        World
        <div></div>
        <div></div>
    </div>
</div>

CSS

* {
    -moz-box-sizing: border-box;
    -webkit-box-sizing: border-box;
    box-sizing: border-box;
}

.left_wrap {
    float: left;
    width: 30%;
    border: 2px solid #000;
}

.right_wrap {
    float: left;
    width: 70%;
    border: 2px solid #000;
}

.right_wrap > div {
    border: 3px solid #ff0;
    height: 100px;
}