Answer
$84$
Work Step by Step
We know that for a matrix
\[
\left[\begin{array}{rrr}
a & b & c \\
d &e & f \\
g &h & i \\
\end{array} \right]
\]
the determinant is $D=a(ei-fh)-b(di-fg)+c(dh-eg).$
Hence here $D=8(3\cdot4-(-1)\cdot6)-0(1\cdot4-(-1)\cdot(-2))+(-5)(1\cdot6-3\cdot(-2))=8\cdot18-0\cdot2-5\cdot12=144-60=84.$
