## Algebra and Trigonometry 10th Edition

$84$
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 $D=8(3\cdot4-(-1)\cdot6)-0(1\cdot4-(-1)\cdot(-2))+(-5)(1\cdot6-3\cdot(-2))=8\cdot18-0\cdot2-5\cdot12=144-60=84.$