Problem: Mr. Jacobs can correct 150 quizzes in 50 minutes. His student aide can correct 150 quizzes in 75 minutes. Working together, how many minutes will it take them to correct 150 quizzes?

My solution:

150q/50m = 15/5=3x

150q/75m= 2x

2x+3x=5x=150

x=30 ..lol