Answer
$\dfrac{1}{x^{15}}$
Work Step by Step
(i) $a^m \cdot a^n = a^{m+n}$
(ii) $\dfrac{a^m}{a^n}=a^{m-n}$
(iii) $a^{-m} = \dfrac{1}{a^m}, a \ne 0, m \gt0$
(iv) $(a^m)^n=a^{mn}$
Use rule (ii) to find:
$=(x^{7-2})^{-3}
\\=(x^5)^{-3}$
Use rule (iv) to find:
$=x^{5(-3)}
\\=x^{-15}$
Use rule (iii) to find:
$=\dfrac{1}{x^{15}}$
