Do you mean "not much time left until the battery is discharged" or "not much time left until I have to turn this in"? If the former, why not just wait until it is discharged and see? If this is class work why have you not tried anything yourself? Do you not know what "mAh" and "mA" mean? If you do, what operation you need to do should be obvious!
(If you have to drive 100 miles and are averaging 50 miles per hour, how long will it take? Do you understand what arithmetic operation you need to do? Do you see how this is conntected to your problem?)