The best way to solve problems like this is to add the hours, then the minutes. Adding 2 hours to 1:15 is 3:15. Adding 51 minutes to that would be 3:66, but 66 is over sixty, so it's an invalid amount of minutes. Therefore, you'd subtract 60 of those minutes and add 1 more hour, for a result of 4:06 PM. :)
