单选题 The sum of the ages of Doris and Fred is y years．If Doris is 12 years older than Fred，how many years old will Fred be y years from now，in terms of y?

A、 y-6
B、 2y-6
C、 (y/2)-6
D、 (3y-2)-6
E、 (5y/2)-6

【正确答案】 D

【答案解析】Let D and F represent Doris’s and Fred’s current ages, respectively. It is given that D + F=y and D = F+ 12. It follows that (F+ 12) + F=y and

. Therefore, Fred’s age y yea’s from now will be