JSFiddle - React, Tailwind, and code Playground
HTML
<div class="wrapper">
<div class="left">left</div>
<div class="main"><textarea name="" cols="" rows=""></textarea></div>
</div>CSS
.wrapper{display:table; width:100%; }
.left{width:20%; background:#cccccc; display:table-cell;}
.main{width:80%; background: gray; display:inline; }
.main > textarea{width:inherit;}