Precalculus (6th Edition) Blitzer

$-22$
The general formula to calculate the determinate of a $2 \times 2$ matrix which has 2 rows and 2 coulmns is $D=\begin{vmatrix}a&b\\c&d\end{vmatrix}=ad-bc$ Now, $D=\begin{vmatrix}1&-3\\-8&2\end{vmatrix}=2-24=-22$