Q. At present, the mothers age is three times the daughter’s age. After twelve years the age of the mother will be twice of her daughter. At present what is the daughter’s age ?

Explanation:

Let the daughter’s present age be D years. Then the mother’s present age is 3D.
After 12 years: mother’s age = 3D + 12, daughter’s age = D + 12.
Given: 3D + 12 = 2(D + 12)
=> 3D + 12 = 2D + 24
=> D = 12.
Check: Mother now = 36; after 12 years, 48; daughter after 12 years, 24; 48 = 2 × 24. Hence, the daughter’s present age is 12 years.