title: Nested calc operations
body: <p>Hopefully this is quite simple. I want to use the CSS calc operation to perform two calculations:</p>
  
  <p>I want to set my width to the equivalent of</p>
  
  <pre><code>(100% / 7) - 2
  </code></pre>
  
  <p>However if I try to perform more than one operation in a CSS calc operation, it fails:</p>
  
  <pre><code>width: calc((100% / 7) - 2);
  </code></pre>
  
  <p>How can I perform multiple calc operations in one CSS statement?</p>