Lil' x and y are variables and big X and Y are functions. So take for example the first part of the first one: rearranging I get: which you can solve for by finding an integrating factor. Same dif' for the other ones in X.
Thanks...care to walk me through it? This isn't a HW problem; I'm preparing for an exam so I need to see how it's done. I had about a 2-year break from Calculus so there's some basic stuff I forget how to do (like integrating factors).