A Father's age is three times the sum of ages of his two children. After 5 years his age will be twice the sum of ages of two children. Find the age of father.

Let the father's age be x.
Let the ages of his children be y and z.
Given x = 3(y + z) -----(1)
After five years, x + 5 = 2(y + 5 + z + 5)
x + 5 = 2(y + z + 10) -----(2)
From (1) and (2):
x + 5 = 2(x/3 + 10)
x + 5 = 2x/3 + 20
x/3 = 15
x = 45
Present age of father is 45 years.