Answer
$$\frac{1}{n^{3}}$$
Work Step by Step
To divide powers of the same base $n$, subtract the exponents of $n$:
$$\frac{n^{3}}{n^{6}}=n^{3-6}=n^{-3}.$$
If the resulting exponent of $n$ is negative, then the expression is equivalent to the reciprocal of $n$ raised to the that same positive exponent:
$$n^{-3}=\frac{1}{n^{3}}.$$
