## Prealgebra (7th Edition)

$\frac{1}{99}$
When $x=\frac{5}{11}$ and $y=\frac{4}{9}$: $x-y$ $=\frac{5}{11}-\frac{4}{9}$ $=\frac{5\times9}{11\times9}-\frac{4\times11}{9\times11}$ $=\frac{45}{99}-\frac{44}{99}$ $=\frac{1}{99}$