If 50% of (x-y) = 30% of (x+y), then what percent of x is y?	Pick one: A) 20 % B) 30 % C) 25 % D) 15 % E) 50 %

Rationale: "50 % of ( x - y ) = 30 % of ( x + y ) 50 / 100 ( x - y ) = 30 / 100 ( x + y ) x = 4 y required percentage = y / x * 100 = y / 4 y * 100 = 25 % answer is c"
Answer: C