Question 288041
Take this in two steps

First step is to evaluate (3 ¥ 5)

Plug 3 and 5 into the definition for ¥ 
(A+B)/2
(3+5)/2
8/2 = 4
So, (3 ¥ 5) = 4

Now take that result and plug it into the original equation
(3 ¥ 5) ¥ 8
4 ¥ 8

Now evaluate that using the definition for ¥ 

(A+B)/2
(4+8)/2
12/2 = 6

The result is 6. Answer B