Answer
$-18$
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, $D=a(ei-fh)-b(di-fg)+c(dh-eg).$
Hence here $D=1(-6-(-8))-0(18-8)+5(-6-(-2))=1(2)-0(10)+5(-4)=2-0-20=-18$
