You are given a math word problem and you are supposed to apply addition or subtraction mathematical operators on the numbers embedded in the text to answer the following question and then only report the final numerical answer.

64 children were riding on the bus . At the bus stop , some more children got on the bus . Then there were 78 children altogether on the bus . How many children got on the bus at the bus stop ?
14

While on vacation , Megan took 15 pictures at the zoo and 18 at the museum . If she later deleted 31 of the pictures , how many pictures from her vacation did she still have ?
2

For homework Amy had 18 math problems and 6 spelling problems . If she can finish 4 problems in an hour how long will it take her to finish all the problems ?
6