There are 60 minutes in an hour, so if the play started at 8:12 subtract 12 from 60 to know how long it is from 8:12 to 9.
60-12 is 48 so it is 48 minutes from 8:12 to 9. From 9 to 10 it is one full hour, and then since it ends at 10:05 you have 5 extra minutes. Add 5+48 which is 53 and then you have 53 minutes and a full hour. So play rehearsal lasted an hour and 53 minutes.