Answer
$\dfrac{b^{17}}{9a^{6}}$
Work Step by Step
Using laws of exponents, then,
\begin{array}{l}
\dfrac{3^{-2}a^{-2}b^{12}}{a^{4}b^{-5}}
\\\\=
\dfrac{a^{-2-4}b^{12-(-5)}}{3^{2}}
\\\\=
\dfrac{a^{-6}b^{17}}{9}
\\\\=
\dfrac{b^{17}}{9a^{6}}
.\end{array}
