More math!? Not quite... you don't need to know a bit of algebra to find the answer to this puzzle. Good luck!

IF B = I 3
AND H = I - I
THEN M = ?

Here is the SOLUTION.

THE SOLUTION:

M = I V I

The equations are simply graphic representations of the variables given.

When the characters are squeezed together, I3 is visually similar to the letter B, and I-I looks like the letter H.  IVI most closely represents M.

NOTE: If you chose something similar but different (say, NI or I\/I) I'd certainly consider that to be a correct response.