Answer:
11 minutes.
Step-by-step explanation:
To print 500 pages the first printer takes 20 minutes.
Then in one minute it can print [tex]\frac{500}{20} = 25[/tex] pages.
Again, to print 500 pages the first printer takes 25 minutes.
Then in one minute it can print [tex]\frac{500}{25} = 20[/tex] pages.
So, working together both the printer will print (20 + 25) = 45 pages in 1 minute.
Therefore, they will print 500 pages in [tex]\frac{500}{45} = 11.11[/tex] minutes ≈ 11 minutes. (Answer)