Oh, so close!  You must have forgotten to carry the one because the correct answer is 42.

I recommend starting with Volume 1 of the Learn Math Fast System.  That book will teach you how to add double digit numbers.  Plus you'll learn a bunch of great tricks to make math easier to solve.  Older students can complete that book in about one month.  Younger students will need more time.  Use the coupon code PT2026 to get 10% off your order.