Let the present age of son be x.
So the present age of father = 3x + 3
After 3 years,
age of son = x+3
and Age of father=3x+3+3 ....(1)
but According to the question
the Age of father after 3 years = 2(x+3) + 13 .....(2)
comparing equation (1) and (2)
3x + 3 +3 = 2(x+3) + 13
3x + 6 = 2x + 19
x = 13
So, Father's present age = 3x + 3 = 42
Age of son after 4 years = 13 + 4 = 17
Age of father after 4 years = 42 + 4 = 46