The sum of ages of father and son is 50 years. Five years ago, father was 7 times as old as son. What is father’s present age?

Explanation

Let father = F, son = S. F + S = 50. Five years ago: (F – 5) = 7(S – 5) => F – 5 = 7S – 35 => F = 7S – 30. Substitute: 7S – 30 + S = 50 => 8S = 80 => S = 10. F = 40 years.