A= (a+b)/2*h
A=(12+15)/2*5
A=(27/2)*5
A=13.5*5
A=67.5in
36/40 would be close to 1
It can be turned into a mixed number: 
hope that helps :) ✨
Answer:
-1280
Step-by-step explanation:
10, -20, 40, -80, 160, -320, 640, -1280
The pattern of the sign is positive, negative, positive, so the 8th term is negative. Then the rule is times 2.