Answer
$\frac{1}{6^{10}}$
Work Step by Step
According to the quotient rule for exponents, $\frac{a^{m}}{a^{n}}=a^{m-n}$ (where $a\ne0$).
Therefore, $\frac{6^{-3}}{6^{7}}=6^{-3-7}=6^{-10}$.
Furthermore, the definition of negative exponents tells us that $a^{-n}=\frac{1}{a^{n}}$.
Therefore, $6^{-10}=\frac{1}{6^{10}}$.