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

Example Input: Problem: in an election between two candidates , one got 60 % of the total valid votes , 30 % of the votes were invalid . if the total number of votes was 9000 , the number of valid votes that the other candidate got , was :
Example Output: 2520

Example Input: Problem: a car traveled 560 miles per tankful of gasoline on the highway and 336 miles per tankful of gasoline in the city . if the car traveled 6 fewer miles per gallon in the city than on the highway , how many miles per gallon did the car travel in the city ?
Example Output: 9

Example Input: Problem: a train running at the speed of 60 km / hr crosses a pole in 15 sec . what is the length of the train ?
Example Output:
250