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

Example Input: Problem: how many prime numbers are between 51 / 13 and 89 / 9 ?
Example Output: 2

Example Input: Problem: a train traveling at 72 kmph crosses a platform in 33 seconds and a man standing on the platform in 18 seconds . what is the length of the platform in meters ?
Example Output: 300 meters

Example Input: Problem: a person travels equal distances with speeds of 3 km / hr , 4 km / hr and 5 km / hr and takes a total time of 54 minutes . the total distance is ?
Example Output:
3.4 km