JSFiddle - React, Tailwind, and code Playground

HTML

<div id="outer">
    <div id="jow">
      jow
    </div>
    <div id="dudes">
      dudes
    </div>
</div>

CSS

#outer {
  display: flex;
  width: 100%;
  border: 1px red solid;
}

#jow {
  flex: 1 1 auto;
}

#dudes {
  border: 1px green solid;
}