Good for you helping him out! Math can be tricky for some kids for sure.
We homeschool, so I know how that is. The moment when they have their 'AHA!' and everything clicks is amazing. The trick is being able to break it down to where they understand and it makes sense to them. Its more than just memorizing a formula, if you want it to stick, they have to understand WHY they are doing it.
Darn it, I just realized this is an old post. Ill go find a new one to upvote! Happy weekend!