cook

This can be done while gaming. Use a crock pot and oven.

clean your house

Literally takes 20 minutes a week with a one bedroom apartment. Run a dishwasher for dishes, spend the 20 cleaning the restroom and vacuuming/dusting.

do your laundry

Thow clothes in the washer and set a timer then play games.

go grocery shopping

Have a list and go once every two weeks. You're single with no kids and can stock the entire refrigerator and freezer. Go grocery shopping at 5am so you can avoid all the slow old people and people blocking isles talking.

clean up after your pets (if you have any)

Don't have any.

get some exercise

Buy a treadmill or exercise bike and throw it in front of the TV. You can now game with a controller while doing aerobics.

pay bills

I work 9 hours a day to do this already.

repair something around the house/car, etc?

Just pay someone who does it for a living to do it.

4+8 = 12. Most people have 15 or so not sleeping/preparing to sleep hours. This isn't hard. I game 3 hours a day and spend 2 hours a day on online college. This does change with hobbies in the summer.