Let son's present age = x.

So father's present age = 3x

Son's age twelve years ago = x-12
Father's age twelve years ago = 3x-12 

(Father's age 12 years ago) = 6 times (son's age 12 years ago)

or

                      3x-12 = 6(x-12)

Solve that and get x = 20

So the son's present age is x, or 20, and the father's present age
is 3x or 3(20) = 60.

Checking: 12 years ago, the son was 20-12 or 8, and the father was 
60-12 or 48, and 48 is indeed 6 times 8.

Edwin