The overall age of X and Y is 11 year greater than the overall age of Y and Z. Z is how many decades younger that X?  Choose the most appropriate option
A) 11
B) 15
C) 12
D) 17
E) 19

Rationale: "a 11 ( x + y ) â € “ ( y + z ) = 11 x â € “ z = 11"
Answer: A