\[\frac{\frac{1}{\text{xy}} - \frac{1}{y} + \frac{1}{x}}{1 - x + y}\ \ :\frac{x}{y} =\]
\[= \frac{\frac{1 - x + y}{\text{xy}}}{1 - x + y}\ :\frac{x}{y} =\]