Question

father’s age is three times the sum of the ages of his two children, but 20 years hence his age will be equal to the sum of their ages. Then the father’s ageis

Answer 1

Let the sum of his children's age =X
Let father's age = Y

From the sum, Y=3x

20 years hence means after 20 years,
So Y +20 =X +40

As the age of both of his children will increase by 20

So, 3X +20 = X+40
2x =20
X = 10

So father's present age is 30years

Hope this helps you.