JSFiddle - React, Tailwind, and code Playground

HTML

<div class="wrap">
    <div class="left_wrap"></div>
    <div class="right_wrap"></div>
</div>

CSS

* {
    -moz-box-sizing: border-box;
    -webkit-box-sizing: border-box;
    box-sizing: border-box;
    
    /* Resets */
    margin: 0;
    padding: 0;
}

.wrap:after {
    clear: both;
    display: table;
    content: "";
}

.wrap > div {
    min-height: 300px;
}

.wrap .left_wrap {
    width: 30%;
    float: left;
    border: 3px solid #f00;
}

.wrap .right_wrap {
    border: 3px solid #000;
    width: 70%;
    float: left;
}