Four years ago a man was 6 times as old as his son. After 16 years he…

Let the present age of man be M years and his son be S years.

According to the question:

M - 4 = 6 (S - 4)

M - 4 = 6S - 24

M = 6S - 20 ------1st equation

M + 16 = 2(S + 16) 

M + 16 = 2S + 32 -------2nd equation

Putting (1) in the (2) equation

6S - 20 + 16 = 2S + 32

4S = 36

S = 9

M = 6S - 20 i.e. 54 - 20 = 34

So, the age of son is 9 years, and the age of father is 34 years