JSFiddle - React, Tailwind, and code Playground

HTML

<div class="c">
<span class="one">123</span>
<span class="two">456</span>
</div>

CSS

.c {
  display: flex;
  flex-wrap: wrap;
  background: gold;
  justify-content: center;
}

.one {
  text-align: center;
  background: red;
  flex-grow: 1;
  min-width: 500px;
}

.two {
  text-align: center;
  background: blue;
}