The task is to generate the correct answer for a given math problem.

Example Input: Problem: a train passes a station platform in 30 sec and a man standing on the platform in 20 sec . if the speed of the train is 54 km / hr . what is the length of the platform ?
Example Output: 60

Example Input: Problem: after decreasing 24 % in the price of an article costs rs . 684 . find the actual cost of an article ?
Example Output: 900

Example Input: Problem: a man is 12 years older than his brother . in two years , his age will be twice the age of his brother . the present age of his brother is :
Example Output:
10