Answer:
4 and 1/2 hours or 270 minutes
Explanation:
Each student spend 30 minutes to set up the puppet show.
+30
They spent twice as long to put everything away.
+30 +30
Current total: 90 minutes
The show was open for three hours
+180 (60 minutes in an hour x 3 hours)
Current total: 270
Total: 270 minutes
OR
Divide 270 by 60 minutes in an hour, which would be 4.5 hours.