P1 takes 12 hrs
Rate for P2P3 together = 1/20 + 1/20 = 1/10
Therefore they take 10
Ratio = 10/1 =
Working alone, Printers X, Y, and Z can do a certain printing job, consisting of a large number of pages, in 12, 20, and 20 hours, respectively. What is the ratio of the time it takes Printer X to do the job, working alone at its rate, to the time it takes Printers Y and Z to do the job, working together at their individual rates?
[A]  4/11
[B]  1/2
[C]  15/22
[D]  10/1
[E]  11/4