To make this easier for us lets first add as many hours needed to get to 12:15.
12-9 = 3
7:30 - 3:00 = 4:30
Now that we are at 12:15 we just add the remainder of the time .
12:15 + 4:30 = 4:45
remember we are dealing with time so after 12 comes 1 unless you are using military time.
It would be 4:45