John was thrice as old as Tom 6 years ago. John will be 2 times as old as Tom in 4 years. How old is Tom today?  Select.
A) 12
B) 14
C) 16
D) 18
E) 20
J-6 = 3(T-6), so J = 3T-12   J+4 = 2(T+4)   (3T-12) + 4 = 2T + 8   T = 16   The answer is 16.
<result>C</result>
John was thrice as old as Tom 6 years ago. John will be 2 times as old as Tom in 4 years. How old is Tom today?