#### Answer

$r$

#### Work Step by Step

$\bf{\text{Solution Outline:}}$
Use the laws of exponents to simplify the given expression, $
r^{-8/9}\cdot r^{17/9}
.$
$\bf{\text{Solution Details:}}$
Using the Product Rule of the laws of exponents which is given by $x^m\cdot x^n=x^{m+n},$ the expression above is equivalent to
\begin{array}{l}\require{cancel}
r^{-\frac{8}{9}+\frac{17}{9}}
\\\\=
r^{\frac{9}{9}}
\\\\=
r^{1}
\\\\=
r
.\end{array}