Use the next properties to simplify the given expression:
[tex]\begin{gathered} \frac{a^m}{a^n}=a^{m-n} \\ \\ a^{-m}=\frac{1}{a^m} \end{gathered}[/tex][tex]\begin{gathered} =\frac{9}{3}a^{2-3}b^{4-(-3)} \\ \\ =3a^{-1}b^{4+3} \\ \\ =3a^{-1}b^7 \\ \\ =3(\frac{1}{a^1})b^7 \\ \\ =\frac{3b^7}{a} \end{gathered}[/tex]