title: Reverse Modulus Operator
body: <p><strong>Over 3 years after asking the question I found the solution.  I have included it as an <a href="https://stackoverflow.com/a/31735393">answer</a>.</strong></p>
  
  <p>I have an expression with modulus in it that needs to be put in terms of x.</p>
  
  <p>(a + x) mod m = b</p>
  
  <p>I can't figure out what to do with the modulus.  Is there a way to get x by itself, or am I out of luck on this one?</p>
  
  <p><strong>Edit</strong>: I realize that I can get multiple answers, but I'm looking for an answer that falls within the range of m.</p>