Can i learn how to play piano when i'm already 20 years of age?

Oh yes, it is never too late to learn! And by all means you should! It would really help you to learn some basic theory, you will have to learn it anyways unless you want to play by ear but I don't recommend that since I'm uming you'll want to be able to master a few peices of music, you'll need to be able to sight read for that. What you can do is go to this website here a href="http://www.teoria.com," rel="nofollow"http://www.teoria.com,/a and take some of the tutorials. I have been through this website and I highly recommend it, you can learn everything you need to know there. I hope this helps you out and good luck with college and the future piano playing!