please help me answer this question! it’s due in soon. could you do this?

I’m not sure what the answer to a is but b is 21

1 + 2 = 3
3+ 3 = 6
6+ 4 = 10
10+ 5 = 15
15 + 6 = 21

The patter is that the number that is added increases by 1 each time

You have to find the angle i don’t know if i i try

The amount used= 13.04- 1.9 = 11.14