When working with time treat it like a math problem and remove the , : ,
So to find out how long it was from 3:45 to 4:30 it would be set up like a usual subtraction problem with 3 digits.
430
-345
---------
Which would be: 85 minutes total.
If you wanted the amount of hours, you would just substract 60 in this case, since there's only one hour in the total
85-60 : Would equal 25, and if you add back the 60 , it would be 1 hour and 25 minutes.
