title: Reverse Number in a Range
body: <p>I've got a servo which turns opposite to the number I get from a program. The numbers I get from the program are between 37...113. I need to convert the 37 to its opposite side. So 37 becomes 113, 38 becomes 112, and so on. 75 stays at 75 because that's the mid point. </p>
  
  <p>Do any of you know of a way to calculate this? This sounds like simple math, but I can't figure it out. I don't want to use a look-up table because the range may change.</p>