Question

Terry has completed 15 homework problems, and Susan has completed 9. Terry is completing 10 problems per hour, and Susan is completing 12 per hour. After how many hours will Terry and susan have completed the same number of problems?

Answer 1

Let the number of hour it took them to have completed the same number of problems be x, then
15 + 10x = 9 + 12x
12x - 10x = 15 - 9
2x = 6
x = 6/2 = 3

After 3 hours, they must have completed the same number of homeworks.