One year ago, Krishna was four times as old as his daughter Kavitha. Six years hence, Krishna's age will be 12 years more than his daughter's age. Find the ratio of the present ages of Krishna and his daughter.

Let Krishna's present age be K and Kavitha's present age be D.
One year ago, Krishna was 4 times as old as Kavitha: K - 1 = 4 (D - 1).....(i)
After Six years , Krishna's age will be 12 years more than Kavitha's age: K + 6 = (D + 6) + 12...(ii)

From the first equation,

K = 4D - 3
From the second equation, K = D + 12.
Equating K ,     

4D - 3  = D + 12

D = 5
K = 4D - 3 = 4 $$\times$$​ 5 - 3 = 17

The ratio of Krishna's present age to Kavitha's present age is 17 : 5. 

Alternate Solution:
Let their ages one year ago be 4x (Krishna) and x (Kavitha).
Present ages: 4x + 1 and x + 1.
Six years hence: 4x + 7 and x + 7, with 4x + 7 = (x + 7) + 12.
=> 4x + 7 = x + 19 => 3x = 12 => x = 4.
Present ages: 4x + 1 = 17, x + 1 = 5 → ratio 17:5.