I believe the answer to 7 would be;
B. 64 cm
This is was a guess. My reasoning is 8(6) =48 and 8(10)=80, so the number in between would be 64.
Another train of thought was the number in the middle of 6 and 10 is 8 and 8(8) = 64
6, 7, 8, 9, 10
X, X, • , X, X
I believe the answer to 8 would be;
C. 82.5 in
Following the equation, you would multiply 15 and 11 the divide the product by two
15(11)=165
165/2=82.5
Please correct me if I am wrong and have a good day!