The overall age of X and Y is 15 year greater than the overall age of Y and Z. Z is how many decades younger that X?
Choose the correct choice from the following answers: A) 11 B) 15 C) 12 D) 17 E) 19

Rationale: b 15 ( x + y ) â € “ ( y + z ) = 15 x â € “ z = 15
Answer: B