JSFiddle - React, Tailwind, and code Playground

HTML

<div class="flex-container">
  <div class="flex-item item1">flex item 1</div>
  <div class="flex-item item2">flex item 2</div>
  <div class="flex-item item3">flex item 3</div>  
</div>

CSS

.flex-container {
  display: flex;
  width: 400px;
  height: 150px;
  background-color: lightgrey;
}

.flex-item {
  margin: 10px;
}

.item1 {
  flex: none; /* Could be omitted? */
  background-color: cornflowerblue;
}

.item2 {
  flex: 1;
  background-color: orange;
}

.item3 {
  flex: 1;
  background-color: green;
}