How to pump tire with cap that won't come off I have a Schwinn bike from probably mid 2000's. The front tire has a regular valve cap that I can twist off and pump with a floor pump. The back tire has an oval cap that I cannot get off. And it seems like it is attached onto a tube, not just a regular valve like the front tire. I can't pull off the cap or twist it off. Not sure how to get it off to pump the tire. 

I don't bike a ton and am not sure if I am using the right terminology. It might be too vague but if anyone knows what I am talking about I appreciate the advice!
Judging by your description you have two different tubes: one with Presta valve and the other with Schreder valve. Both should have protective plastic caps that should pretty easily come off. It might be possible that cap on the rear wheel valve is stuck so some pliers might help to unscrew it. 

Regarding pumping tires, your floor pump should have adapter for both valve types so you should use one that fits. 

Maybe, if you have pump for only one valve type, you could consider changing your tubes to be of the same type (that matches the pump). Anyway, it is recommended to change tubes because they get porous and leak air (especially if they are too old).