When you are adding you are ,say you have the number 4 and you need to add it to 5 you are basically mushing those two numbers together and seeing what you get, and I got 9. with multiplying you are multiplying it by itself however many times you need to, to find out the answer. :)
A. just gave you the answer
The answer is 228. (I know late, but for others I guess)
Midpoint of (x1,y1) and (x2,y2) is

so the midpoint of HX is the mdpoint of (13,8) and (-6,-6)
which is



the midpoint is (3.5,1)