title: LESS: Subtract from variable
body: <p>Using LESS, how can I subtract values with "px" at the end of the variable. I have the following variable:</p>
  
  <pre><code>@bpMobile: 600px
  </code></pre>
  
  <p>What I want to do is subtract this by 1px</p>
  
  <pre><code>@media only screen and (max-width: @bpMobile - 1px ) {
  }
  </code></pre>
  
  <p>How can I achieve this with LESS?</p>