Calculate $\frac{9}{4}$ to the power of $-2$ and get $\frac{16}{81}$.
$$sort(-\frac{1}{27},\frac{16}{81})$$
Least common denominator of the numbers in the list $-\frac{1}{27},\frac{16}{81}$ is $81$. Convert numbers in the list to fractions with denominator $81$.
