#### Answer

$-8$

#### Work Step by Step

$det=\begin{vmatrix} 3 & 12 & -1 \\ 5 & 9 & 0 \\-6 &4 & -2 \end{vmatrix} \begin{matrix} 3 & 12 \\ 5 & 9 \\-6 &4 \end{matrix}$
$=[(3)(9)(-2)]+[(12)(0)(-6)+[(-1)(5)(4)]-[(-6)(9)(-1)+(4)(0)(3)+(-2)(5)(12)]]$
$det=-54+0-20-(54+0-120)$
$det=-74+66=-8$