[tex] \frac{x}{y} = d \\ \frac{y}{z} = \frac{1}{d} \\ \frac{y}{z} = \frac{1}{ \frac{x}{y} } \\ \frac{y}{z} = \frac{y}{x} \\ \frac{1}{z} = \frac{1}{x} \\ z = x \\ \frac{x}{z} = \frac{x}{x} = 1[/tex]