The overall age of X and Y is 19 year greater than the overall age of Y and Z. Z is how many decades younger that X?  Pick:
A) 11	B) 15	C) 12	D) 19	E) 20

Rationale: "d 19 ( x + y ) â € “ ( y + z ) = 19 x â € “ z = 19"
Answer: D