I've discovered that 10 + 3 = 13 is a relatively difficult problem for Monkey at this point; he hasn't caught the concept of placevalue yet. Which isn't very surprising, since it's a pretty new idea, this writing of numbers and matching them with their correct meanings. I realized this as we were doing some problems at Khan Academy. I like a lot of things about Khan, but there isn't much explanation or practice in the arithmetic section. It jumps from single digit problems to triple digit with no in between, and relies heavily on number lines. But as a supplement, to see how he's doing, and what happens when I sit back and let him do his thing, it's wonderful. So now, we're working a bit on some of the ideas that I've realized are weak. I thought that I might share the lab sheet I made up for him. To use it, copy, then paste into your word processor. Let me know how it goes for you!