The sum of ages of Kartik and his father is 35 years. When Kartik’s age will be equal to present age of his father , then sum of their ages…

30 years

Let Kartik’s age be X and his father’s age be Y.
Given , at present , X+ Y = 35 years
Sum of their ages will be 85 years after = (85 – 35) / 2 = 25 years
So,Kartik’s current age = ( 35 – 25 ) / 2 = 5 years
Therefore, present age of father = 35 – 5 = 30 years