Can't get bike valve caps off I will sound a bit thick but i'm no bike mechanic, to give you an idea of what make my bike is here are some pics (the bike isn't mine and the owner doesn't know).





the problem is that I cannot get the valve caps off I tried twisting and pulling, pliers are a no no due to the bike not being mine, here's a pic, any help is appreciated, Thanks.



Quick edit
Just to clarify I've not stolen the bike, 
I crashed mine and it's the beginning of summer and I really wanted to ride, the bike is my mother's and just needs some maintenance. Also I appreciate the answers I've tried using more force but the entire valve seems to turn and jam, no movement on the cap. Any ideas?
Turn anti-clockwise as seen from above and use more force. You should be able to get them off by hand.

If you do destroy the caps, go to a bike store and buy replacements. Ask for 'Schrader' type caps. 

Can we assume you are borrowing a bike and need to inflate the tire? The statement 'the bike isn't mine and the owner doesn't know' is slightly troubling. If you have trouble with a borrowed bike take it back to the owner. (deleted as based on misunderstanding.)

Brand and model of bike does not matter, tube valves are either 'Schrader' (same as on car tires) or narrower 'Presta' types.