Answer:
12.68 de
Step-by-step explanation:
C 59.5 because 8.5-1.5 =7 and 10-1.5=8.5 multiply 8.5x7=59.5 formula of the area of the rectangle is Length times width

You can see it's a geometric sequence because the ratio is constant (

).
The nth term of a geometric sequence:


It has to be the sum for term 4 through term 15, so n=4 and the number above the sigma is 15.
Your answer: