There are several ways to solve it. Actually one (creative Google searching) isn't really "solving it" I suppose but it will get you to the solution quickest. I solved it doing the simple math with pencil and paper, admittedly taking too much time. It's not really that hard.
What you have to do is look at the puzzle and relax a little. There is one number with only one possible answer. There is another number with only two possible answers. The hint helps bound the problem so it's less brute force trial and error needed.
FWIW, in the past I've solved similar puzzles by writing a little program that automated everything, which for me was more of a fun exercise than going back to 3rd grade math class. But this time I just did it on paper.
If it's still fun, keep digging away at it. When it gets frustrating, put it down for a few days.