Answer:
It is the first choice.
Step-by-step explanation:
This is a sequence where
the next term is obtained by adding 6.
first term = -9 + 6(0) = -9
second term = -9 + 6(1) = -3
third term = -9 + 6(2) = 3
4th term = -9 + 6(3) = 9
and 81 = -9 + (6*15).
So the answer is Sigma (-9 + 6n) from n= 0 to n = 15.