To add or subtract expressions, expand them to make their denominators the same. Multiply $11$ times $\frac{z}{z}$.
$$\frac{504}{\frac{9}{z}+\frac{11z}{z}}=36$$
Since $\frac{9}{z}$ and $\frac{11z}{z}$ have the same denominator, add them by adding their numerators.
$$\frac{504}{\frac{9+11z}{z}}=36$$
Variable $z$ cannot be equal to $0$ since division by zero is not defined. Divide $504$ by $\frac{9+11z}{z}$ by multiplying $504$ by the reciprocal of $\frac{9+11z}{z}$.
$$\frac{504z}{9+11z}=36$$
Variable $z$ cannot be equal to $-\frac{9}{11}$ since division by zero is not defined. Multiply both sides of the equation by $11z+9$.
$$504z=36\left(11z+9\right)$$
Use the distributive property to multiply $36$ by $11z+9$.
