when I first tried this problem I tried seeing how many ways there were to go up with a smaller no. of steps. I finally got the formula: 2 to the power of n. So I did 2 to the power of 10 (no. of steps) and got 1024 (no. of ways to go up 10 steps) . Then I checked the solution and it said there were 89 ways to go up 10 steps! I don't understand what I did wrong!? can somebody please explain??