Every hour has 60 minutes. If you add 48 minutes from the second time and 25 from the first time, it will give you 73 minutes. If you subtract that by 60 then it will give you 13 minutes. Since 73 was greater than 60, you gain another hour. If you add 4, 2, and that one additional hour, it will be 7 hours. In the end it is 7 hours and 13 minutes. Hope this helps! :)