Mr. Tough can grade the final exams in 12 hours. His assistant, Ms. Nice, can grade the same exams in 15 hours. What fraction of the exams can Mr. Tough grade in 1 hour, without any help? This is impossible. Please help me. I spent sooo loong on this and got it wrong. I don't have many points. Sorry about the 20 points. IT IS VERY URGENT!!!!!!!!!!!!!!!!!
