If a/x = 1/3 and a/y =1/ 4, then (x + y) =  Select the correct option:
A) 2 a
B) a / 2
C) 6 a
D) 7 a
E) 9 a

Rationale: ratio 1 : 3 a = x ratio 2 : 4 a = y x + y = 7 a answer is d
Answer: D