Let son's age be x
Father's age is x^2
In 20 years, son's age = x + 20
Father's age = x^2 + 20
The second statement can be expressed as


This is a quadratic equation which can be solved through factorization.



So the 2 solutions are
x - 8 = 0, or x = 8
x + 5 = 0, or x = -5
Since age has to be positive, the son's age is  and therefore
the father's age is .
In 20 years age, son's age will be 28 and father's age will be 84.
28*3 = 84 (correct!)
:)