To divide fractions, multiply the first fraction by the reciprocal of the second fraction.

Simplify common factors before multiplying.

$$\frac{5}{\cancel{6}_1} \times \frac{\cancel{12}^2}{7} = \frac{5 \times 2}{1 \times 7}$$

$$\frac{10}{7}$$

The final answer is $\boxed{\frac{10}{7}}$.

Simplify common factors (16 and 18 are both divisible by 2).

$$\frac{\cancel{16}^8}{15} \times \frac{1}{-\cancel{18}_9} = \frac{8 \times 1}{15 \times (-9)}$$

$$\frac{8}{-135} = -\frac{8}{135}$$

The final answer is $\boxed{-\frac{8}{135}}$.

$$\frac{-72}{-5} = \frac{72}{5}$$

The final answer is $\boxed{\frac{72}{5}}$.