If your toilet bubbles when you drain the tub it is more than likely a main line partial stoppage. My suggestion if you have never run a sewer snake before call a plumber. Those snakes are very powerful and if you get it caught it can cause serious injury. It could also be a vent stoppage which means you might have to go on the roof to clear it depending on the design of your system. If you decide to do this yourself be very careful.The tub is slow to drain, i will try to unclog the tub and see if the bubbles go away.
Thanks for the help!