title: SML operator and operand do not agree
body: <p>I am trying to write my first function in sml. It takes a tuple and returns the sum of first element times 10, second element times 6 and the third, and then divides by 10. I don't know what I am doing wrong here I get this error operator and operand do not agree [tycon mismatch].</p>
  
  <pre><code>fun rgb2gray(rgb: (int*int*int))=
  let
      val x = (#1rgb * 3 )+ (#2rgb * 6 )+ (#3rgb)
  in  
      x=x/10
  end
  </code></pre>