Question 427519
Let X be the amount of hours it takes the newer machine to fold, stuff, and address a particular mailing.  The old machine can process the mailing in 6 hours, or do 1/6 mailing per hour.  Together the machines can finish the job in 2 hours, or process 1/2 the job per hour.  Thus:

1/6+1/x = 1/2
1/x = 1/2 - 1/6
""""= 3/6 - 1/6
""""= 2/6 = 1/3
1/x = 1/3
x = 3

Thus the new machine takes only 3 hours working by itself to finish the job.