It would be 8 hours and 43 minutes.
To do this you add 15 minutes to the 6:45 am to get 7:00 am and add 8 hours from there to get to 3:00 pm. Then you add the 28 minutes you need to get to 3:28. You then combine the 15 minutes and the 28 minutes to get 43 minutes. Lastly, add the 8 hours and you get 8 hours and 43 minutes!
