Answer
$-10$
Work Step by Step
The determinant of a $2 \times 2$ matrix can be computed by using the formula $det =ps-qr$
where $det =\begin{bmatrix}p & q \\r & s\end{bmatrix}$
We have $det =\begin{bmatrix} -1 & 0 & 0 \\0 & 5 &0 \\ 0 & 0 & 2 \end{bmatrix}$
or, $det =-1 \begin{bmatrix}5 & 0 \\0 & 2\end{bmatrix}-0+0=-1(10-0)=-10$
