<div class="container">
  <p class="col col--1">First is loooooong.</p>
  <p class="col col--2">Second is looooonger.<br/>…<br/>…</p>
  <p class="col col--3">Third is short.</p>  
</div>
.container {
  display: flex;
  flex-wrap: wrap;
  border: 5px solid black;
  padding: 1em;
}

.col--1 {
  flex: 1;  
}

.col--2 {
  flex: 2;  
}  

.col--3 {
  flex: none;
}

@media (max-width: 00px) {
  .container {
    flex-direction: column;
  }
}

/* etc: */

body {
  margin: 1.5em;
}

.col {
  background: #b3e888;
  padding: 1em;
  margin: 2px;  
}

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.