five years back my age was three times the age of my son. after ten years my age will be double that of my son. what is my present age?

Let the present age of son be x years.
Therefore, the present age of the father = 3x years

After 10 years,
Son's age = (x + 10) years
Father's Age = (3x +10) years

ATQ,
3x + 10 = 2 (x + 10)
=> 3x + 10 = 2x + 20
=> 3x - 2x = 20 - 10
=> x = 10

Therefore, 
Present age of son = 10 years
and, 
Present age of me(father) = 3 *10 = 30 years.