Rinas father is thrice as old as Rina. After 12 years, he will just be twice as old as his daughter. Find the present age of Rina.

The correct answer is 12

Let Rinas presnt age be x
∴ Her fathers age is 3x
After 12 years, Rinas age will be (x + 12) and her fathers age will be (3x + 12)
∴ We can write the equation as follows
3x + 12 = 2(x + 12)
∴ 3x + 12 = 2x + 24
∴ 3x - 2x = 24 - 12
∴ x = 12
∴ Rinas present age = 12 years