Ritesh is 12 years older than the Mohit. 17 years ago. Ritesh's age was four times of Mohit's age. Mohit's present age (in years) is: 

Correct option is C

Given: 

Ritesh is 12 years older than Mohit

17 years ago, Ritesh's age was four times Mohit's age  

Solution: 

Let the Present age of Ritesh is R and Mohit is M 

Then, From first condition;

R = M + 12 ....(1) 

From second condition;

R - 17 = 4(M - 17) 

R - 17 = 4M - 68 

Putting the Value of R from eq(1)

M + 12 - 17 =  4M - 68 

M - 5 = 4M - 68 

3M = 63 

M = 21 

Thus , Mohit present age is 21 years.