Need help with economics homework!!!!?

Okay so I know how to find the AFC and AVC. But I'm trying to figure out the Average Total Cost (ATC) and i see that the formula is TC/Q (output) = TFC/Q + TVC/Q = AFC +AVC. My question is, HOW IN THE HECK DO I FIND THE OUTPUT?! THis is driving me crazy! I know that "Q" represents the output but how do I find it? PLEASE help me if you know. It will make everything so much easier. Thanks so much!