JSFiddle - React, Tailwind, and code Playground

HTML

<div id="parent">
        <div id="leftdiv">left content</div>
        <div id="rightdiv">right content</div>
      </div>

CSS

#parent {
      border: 1px solid red;
      width: 100%;
      display: flex;
   }
   #leftdiv {
      
      border: 1px solid blue;
      width: 100px;
      height: 200px;
      flex:none;
   }
   #rightdiv {
      flex:1;
      background: tomato;
      border: 1px solid green;

      height: 200px;
   }