Consider the rational expression below.  

$( \frac { 1 } { y } - \frac { x } { y } ) ( \frac { 1 } { x } + 1 )$

1. Set the expression equal to $10$ and solve for $y$.

    Step (a):

   $\left(\frac{1-x}{y}\right)\left(\frac{1+x}{x}\right)=10$

2. Set the expression equal to $0$ and solve the equation.

   Step 1 (b):

   $\left(\frac{1-x}{y}\right)\left(\frac{1+x}{x}\right)=0$

   Step 2 (b):

   $(1-x)(1+x)=0$

3. Rewrite the expression as a single fraction in simplified form.