I'm going to change all of the hours to 24-hour time to make calculating easier.
7:00 am is still 7:00
9:00 pm is 9+12=21:00
In between 7:00 and 21:00, there are 21-7=14 hours.
Now, since he took off an hour for lunch, we get 14-1=13 hours.
Joe worked for 13 hours.
Good luck!
