so, my motherboard is the asrock z77 pro3. I already have1 stick of 8GB DDR3 RAM clocked at 1333Mhz, but i want to know if its possible to run that AND 2x2GB DDR3 clocked at 1333 at the same time, resulting in 12GB
Can try yes, would go with the 8GB in slot 1 (channel A) and the 2x2 in slots 3-4 (channel B), then if they do play you would effectively have 8GB running in dual channel and the odd 4 from the 8GB stick in single channel mode. Keep in mind there are no guarantees that they will play
Should be able to, yes. You may loose dual channel mode on all or some memory with only a single stick in the second set of slots. It will depend on the board.
Can try yes, would go with the 8GB in slot 1 (channel A) and the 2x2 in slots 3-4 (channel B), then if they do play you would effectively have 8GB running in dual channel and the odd 4 from the 8GB stick in single channel mode. Keep in mind there are no guarantees that they will play