title: Adding units to font-size and line-height variables in font shorthand
body: <p>I try to learn SASS. In order to compile my files, I use Prepros app. It worked well until I started to use mixins. My code is as follows:</p>
  
  <pre><code>@mixin fontface($size) {
      font: ($size)px/($size*1.7)px "Roboto Slab", Georgia, sans-serif;
  }
  </code></pre>
  
  <p>And I use it like this:</p>
  
  <pre><code>@include fontface(28);
  </code></pre>
  
  <p>When I compile it, I got spaces added to variables, like this:</p>
  
  <pre><code>font: 28 px/47.6 px "Roboto Slab", Georgia, sans-serif;
  </code></pre>
  
  <p>How can I change it? Is it because the app, or I am doing something wrong?</p>