Albert is 2 times Mary’s age and 4 times as old as Betty. Mary is 12 years younger than Albert. How old is Betty?  Choose the correct choice.
A) 6 B) 12 C) 10 D) 15 E) 18

Rationale: "a = 2 m = m + 12 m = 12 a = 24 a = 4 b , and so b = 6 the answer is a ."
Answer: A