And now that I look at the problem again, I suddenly realized that it's not a valid problem. In the original ad there was a space after "5 +," and you were supposed to fill it out. Which I just realized is impossible with just the information given.
That's why you need to go to their website and pay lots of money!
http://www.chess.com/forum/view/general/how-does-math-relate-to-chess