$$\frac{x^{3}y^{6}}{x^{5}y^{6}}$$
To divide powers of the same base, subtract the denominator's exponent from the numerator's exponent.$$x^{3-5}y^{6-6}$$
Subtract $5$ from $3$.$$x^{-2}y^{6-6}$$
Subtract $6$ from $6$.$$x^{-2}y^{0}$$
For any number $a$ except $0$, $a^{0}=1$.$$\frac{1}{x^{2}}$$