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

Example Input: Problem: two tains of equal lengths take 10 seconds and 15 seconds respectively to cross a telegraph post . if the length of each train be 120 metres , in what time ( in seconds ) will they cross each other travelling in opposite direction ?
Example Output: 12

Example Input: Problem: 5 years ago , paula was 3 times as old as karl . in 6 years , paula will be twice as old as karl . what is the sum of their ages now ?
Example Output: 54

Example Input: Problem: if in a race of 80 m , a covers the distance in 20 seconds and b in 25 seconds , then a beats b by :
Example Output:
16 m