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

Example Input: Problem: in traveling from a dormitory to a certain city , a student went 1 / 5 of the way by foot , 2 / 3 of the way by bus , and the remaining 10 kilometers by car . what is the distance , in kilometers , from the dormitory to the city ?
Example Output: 62

Example Input: Problem: a can do a work in 15 days and b in 20 days . if they work on it together for 7 days , then the fraction of the work that is left is
Example Output: 11 / 6

Example Input: Problem: two goods trains each 820 m long are running in opposite directions on parallel tracks . their speeds are 45 km / hr and 30 km / hr respectively . find the time taken by the slower train to pass the driver of the faster one ?
Example Output:
78.72