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

Example Input: Problem: in what time will a train 50 m long cross an electric pole , it its speed be 360 km / hr ?
Example Output: 0.5

Example Input: Problem: a number x is mistakenly divided by 10 instead of being multiplied by 10 . what is the percentage error in the result ?
Example Output: - 99 %

Example Input: Problem: the ratio between speed of the two trains is 7 : 8 . if the 2 nd train runs 400 km in 4 hrs , what is the speed of the 1 st train ?
Example Output:
87.5