Question

x^2-9y^2/xy/1/y-3/x

Answer 1

I think you need some parentheses in that horrid run-on expression.

As written it could mean

x^2 - 9y^2/xy / 1/y - 3/x
= x^2 - 9y/x * y/1 - 3/x
= x^2 - 9y^2/x - 3/x
= x^2 - 3(3y^2+1)/x

There are, of course, many other ways to parse all that stuffed jammed together. Unless otherwise specified, + and - signs separate terms.