Answer:
The last term is 33.
Step-by-step explanation:
Sn = (n/2)(a1 + L) where a1 = first term and L = the last.
So:
-480 = (20/2) ( -81 + L)
-480 = 10( L - 81)
L- 81 = -480 / 10 = -48
L = -48 + 81
L = 33.
B
if you look closely, you can see that the side of it goes up 2, then 2, then 1.
It would look like this:
