If 3/w + 3/x = 3/y and wx = y, then the average (arithmetic mean) of w and x is	Choose the correct choice from the following.
A) 1 / 2	B) 1	C) 2	D) 4	E) 8

Rationale: "given : 3 / w + 3 / x = 3 / ywx = y find : ( w + x ) / 2 = ? 3 ( 1 / w + 1 / x ) = 3 ( 1 / y ) - divide both sides by 3 ( 1 / w + 1 / x ) = 1 / y ( x + w ) / wx = 1 / wx - sub ' d in y = wx x + w - 1 = 0 x + w = 1 therefore ( w + x ) / 2 = 1 / 2 ans : a"
Answer: A