Let the present age of the son be x years .
Then, age of the father is 4x years.
Four years later,
age of son will be (x+4) years.
Then age of father will be (4x+4) years.
Acc. to the Question,
After 4 years, the age of father will be 3 times the son's age.
∴ 4x+4 = 3(x+4)
⇒4x + 4 = 3x + 12
⇒4x - 3x = 12-4
⇒x = 8.
Hence, present age of son is x=8 years & the present age of father is 4x=4*8 years or 32 years.