Answer:
9 hours
Explanation:
if they came in at 7:30 a.m and leaves at 11:45 a.m they have been there for 4 hours and 15 minutes.
If they arrive at 12:30 p.m and leave at 5:15 p.m they have been there for 4 hours and 45 minutes
so in total they have been there for 9 hours