それを自分で試してみてください

<!DOCTYPE html>
<html>
<title>W3.CSS</title>
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="/lib/w3.css">
<body>

<h2>Using w3-rest</h2>

<div class="w3-row">
  <div class="w3-quarter w3-container w3-red"><p>quarter</p></div>
  <div class="w3-half">
    <div class="w3-row">
      <div class="w3-col w3-container w3-blue" style="width:20%"><p>80px</p></div>
      <div class="w3-rest w3-container w3-green"><p>rest</p></div>
    </div>
  </div>
  <div class="w3-quarter w3-container w3-purple"><p>quarter</p></div>
</div>
<br>

<div class="w3-row">
  <div class="w3-quarter w3-container w3-red"><p>quarter</p></div>
  <div class="w3-quarter w3-container w3-purple"><p>quarter</p></div>
  <div class="w3-half">
    <div class="w3-row">
      <div class="w3-col w3-container w3-blue" style="width:35%"><p>35%</p></div>
      <div class="w3-rest w3-container w3-green"><p>rest</p></div>
    </div>
  </div>
</div>

</body>
</html>