Thinking Mathematically (6th Edition)

$\frac{9}{11}$
Repeating decimals of the form $0.\overline{a}$, where $a$ is an integer and $10 \le a \le 99$, can be written in fraction form as: $\dfrac{a}{99}$ With $a=81$, the given repeating decimal can be written in fraction form as: $=\frac{81}{99} \\=\frac{9}{11}$