title: Calculate a percent with SCSS/SASS
body: <p>I want to set a width in percentage in scss via calculation, but it gives me errors..</p>
  
  <blockquote>
    <p>Invalid CSS after "...-width: (4/12)%": expected expression (e.g. 1px,
    bold), was ";"</p>
  </blockquote>
  
  <p>I want to do something like</p>
  
  <pre><code>$my_width: (4/12)%;
  
  div{
  width: $my_width;
  }
  </code></pre>
  
  <p>how do I add the % sign in there?</p>
  
  <p>Same question with px and em</p>