title: How do I reverse the modulus operator?
body: <p>So I have this equation: x % a = b. Values a and b are already known. I want to find the value of x. So, how do I reverse plain modulus? Everything I've found was in the order (a + x) % m = b.
  I need to do this for an encryption algorithm. It has a way of knowing what the number is, I just need to separate out the parts of it and this is the only part I haven't reversed.</p>