"I will determine which project requires my attention by the number of hours we are behind and then the project size. I am comfortable delegating tasks when needed, but I am also aware that these times will require an additional commitment of hours from me. Never have I under delivered on a deadline."

Prioritizing is a skill that requires practice. There are many approaches you can take. Here are some suggestions:

1) Make a list. By thinking through and writing down each item that needs completion, you can see it on paper.
2) Mark what is urgent or essential. Take into account deadlines and meetings.
3) Order each task based on effort and estimated value. Considering due dates and how long it will take to do each item (also considering how much time you have).

In answering this question, show the interviewer that you have a system in place that helps you to think through what needs to happen, and when. The better you can prioritize, the more productive you will be, making you an asset to their company!