2. Six years ago, Anna's age was five times her son Mario's age. Now, however, it is three times Mario's age. In how many years will Anna's age be twice Mario's age?
(A) 8
(B) 6
(C) 10
(D) 9
(E) 12
(2) The correct answer is $(E)$.

Let $A$ be Anna's age and $M$ be Mario's age, then $A-6=5(M-6), A=3M$, from which $A=36, M=12$. The difference in age is 24, and Anna's age will be double that of Mario when Mario is 24 years old, which is in 12 years. 

Problem proposed by Paolo Negrini.