If x + y = 8z, then which of the following represents the average (arithmetic mean) of x,y, and z, in terms of z?
(A) 2z + 1
(B) 3z
(C) 5z
(D) z/3
(E) (3z) / 2
Doh! This seemingly easy question stumped me and took me way more than the alloted 2 minutes to figure out.