The best way of answering this sort of question is to use a 24 hour clock as this allows simple subtraction.
6.30 pm in a 24 hour clock is 12.00 (mid day) + 6.30 = 18.30
18.30 - 08.30 = 10
11 hours
8 hours.
4.5 hours
840
Nine and a half hours.
Nine hours.
one hour
how many hours is 6:30pm to 6:30am
ten and a half
4 and 1/2
That would be ten and one half hours.
7 hours and 30 minutes.