Let's map this out mathematically. We'll use x for the age.
A father is twice (2x) as old as his son and the sum of their ages is 90 years.
There's a similar x in there, right? So we can simplify into: and then isolate the variable by dividing the 3 out to get .
Going back to the problem, we know that the father is 2x. We know x is 30 now, so . The son is just x, so he is thirty.
Father = 60 years
Son = 30 years