Sorry. You really don't.
Just follow the instructions in Hint #2. Nobody is going to explain it
to you any better or more clearly than Hint #2 already does.
They even gave you the second drawing, with all of the outside pieces
labeled. Just go around that drawing, one piece at a time. Add up all
of the 'x's, and add up all of the plain numbers, but keep them separate ...
don't mix 'x's with plain numbers. The answer you'll get from a trip around
the drawing is on the list of choices.
