A father is older than his first son by 30 years, the first son is older than the second son by 10 years. If the sum of their ages be 95 years, find the age of father.

Let us assume the age of second son be Y, then age of first son will be Y + 10 and age of father will be (Y + 10 + 30) years respectively;
then according to question,
sum of their ages be 95 years.
x + x + 10 + x + 10 + 30 = 95
⇒ 3x = 95 - 50
⇒ 3x = 45
∴ x = 15
age of the father = x + 10 + 30
Hence, age of the father = 15 + 10 + 30 = 55 years.