Answer
$\dfrac{1}{27}$
Work Step by Step
(i) $a^m \cdot a^n = a^{m+n}$
(ii) $\dfrac{a^m}{a^n}=a^{m-n}$
(iii) $a^{-m} = \dfrac{1}{a^m}, a \ne 0, m \gt0$
Use rule (ii) to find:
$=3^{4-7}
\\=3^{-3}$
Use rule (iii) to obtain:
$=\dfrac{1}{3^3}
\\=\dfrac{1}{27}$
