Question 378045
Suppose the son's age is x years, and the man's age is 9x years.

In 9 years, the son's age will be x+9, and the man's age will be 9x+9 which is three times the son's age.

Therefore we have 9x+9 = 3(x+9) --> 9x+9 = 3x+27 --> x = 3 --> The son is 3 years old and the man is 27 years old.

This seems like the only convenient way to solve the problem -- it is possible using graphing but it is not the best way.