<div class="flex">
  <div class="item">1</div>
  <div class="item">2</div>
  <div class="item">3</div>
</div>
.flex {
  display:flex;
  background-color: lightskyblue;
}

.item {
  flex:0 1 33%;
}

.item {
  background-color: red;
  color:#fff;
  margin: 10px;
  text-align: center;
  padding: 10px;
}

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.