Let s be the son's age 15 yeasr ago and m the mother's age that year.
[tex]s = \dfrac{m}{3}[/tex]
We also know that:
[tex]m = s+30[/tex]
Plotting vallues:
[tex]s = \dfrac{m}{3}\\\\\\3s = s+30\\\\2s = 30\\\\s = 15\\\\m = 45[/tex]
Remember that they were that age 15 years ago.
So their actual age is 30 and 60.
