Out of these equations: which one(s) are the variables not separable? Now I think II and III can be separated but I can not. Is this right? The way I came to this conclusion is by simply testing each one. I could not figure out a way to separate the variables for I. but for II and III I could. I might just be completely missing something for I and maybe it can be separate, maybe the other two can't and I just did them wrong! I'm not sure. As I said I couldn't figure out a way to separate I, but for II I had: d^2y/y*dy= 3x+dx after separating the variables and for III I had: dx/x=y^2/y-dy I'm not confident at all about how I separated them, it just doesn't seem right.