How do you use the laws of exponents to simplify the expression (3a^3 - 6a^6)/a^-1?

$\frac{3 {a}^{3} - 6 {a}^{6}}{a} ^ \left(- 1\right) = \frac{3 {a}^{3} \left(1 - 2 {a}^{3}\right)}{a} ^ \left(- 1\right) = 3 {a}^{3 - \left(- 1\right)} \left(1 - 2 {a}^{3}\right)$
$= 3 {a}^{4} \left(1 - 2 {a}^{3}\right)$.