title: Subract values of 2 arrays and get a new array with subtracted values
body: <p>Basically, I want to do this:</p>
  
  <pre><code>[1,2,3,4,5].some_method([1,5,8,7,8])
  =&gt; [0,-3,-5,-3,-3]
  </code></pre>
  
  <p>What is the best way to do this in Ruby?</p>