Albert is 2 times Mary’s age and 4 times as old as Betty. Mary is 10 years younger than Albert. How old is Betty?
Choose the correct choice from the following answers:
A) 5  B) 8  C) 10  D) 12  E) 15

Rationale: "a = 2 m = m + 10 m = 10 a = 20 a = 4 b , and so b = 5 the answer is a ."
Answer: A