Explanation:

pool : kerosene 

   3  :  2(initially) 

   2  :  3(after replacement)

Remaining Quantity /Initial Quantity = (1−Replaced Quantity/Total Quantity)

(for petrol)   2/3 = (1−10/k)

 = K = 30

 Therefore the total quantity of the mixture in the container is 30 liters.

Hence, option 2 is the correct answer.