Write the times for each hour from start time:
10:25 am
11:25 am
12:25 pm
1:25 pm
2:25 pm
3:25 pm
4:25 pm
5:25 pm
6:25 pm
There are 8 hours between 10:25 am and 6:25 pm.
they finished at 6:15 which is 10 minutes before 6:25 ( 25-15 = 10)
10 minutes less than a full hour is 50 minutes ( 60 - 10 = 50)
8 hours - 1 hour = 7 hours
7 hours + 50 minutes = 7 hours 50 minutes total time.