Ok i know this proberly sounds really stupid but.....
How do you get 3 people playing rainbow six vegas 2 at the same time?
I keep on looking in split screne and it only comes up with the option for 2 people to play.
I have it on xbox 360 so if there is anyone out there that could help me it would be appricated.

you can only get 2 on split screen...if you want all 3 then you have to have 3 separate consoles and be online.

you can only do 2p coop campaign, but youcan do 4p t hunt online

So what do you do to get all 4players to play terrorist hunt together on the same console?

You can't do that. Only 2 people can play co-op on the same console. If you want 4 you have to be on different consoles and play online or through a LAN connection.

But the game case says 2-4 player coop then states sys link 2-16 players

You can do 2 players on campaign, 2 on thunt offline and up to 4 players on thunt online.System link/LAN is the local network which basically means you can hook up multiple consoles on the same local network and play each other.Say you have a friend with a ps3 and you also have one.Your friend brings his to your house and you hook them both up to your network.You would use the system link/LAN option to play each other on the same network but you would be on seperate tvs and consoles.This feature is great for dorms or friends in the same apartment buildings lol.