joint pmf and covariance questions

I hope I have put this in the right section, technically I am doing this at uni but its pretty easy but for some reason I just don't know how to do it...

Anyway, I am having a bit of trouble using tables to find covariance and variance. This question is just an example I am stuck on from a previous exam where:

http://i77.photobucket.com/albums/j60/shhusan/table.jpg

I don't really understand how to find: C(X,Y), Var(X), Var(Y) or C(X+3Y-1,X-2Y). The formula I have confuse me even more. Any help would be greatly appreciated.