title: SASS: width: 100% - 20px - is it possible?
body: <p>I use padding in many of my projects, and it would be handy if I could substract the padding from the width, it is possible ? </p>
  
  <p>if:   </p>
  
  <pre><code>width:100%; 
  </code></pre>
  
  <p>and </p>
  
  <pre><code>padding: 20px; 
  </code></pre>
  
  <p>= </p>
  
  <pre><code>100% - 40px ?  
  </code></pre>