# How do you find the determinant of |(13,7), (-5,-8)|?

$| \left(13 , 7\right) , \left(- 5 , - 8\right) | = - 69$
$\det \left(\begin{matrix}13 & 7 \\ - 5 & - 8\end{matrix}\right) = | \left(13 , 7\right) , \left(- 5 , - 8\right) |$
$= \left(13\right) \left(- 8\right) - \left(- 5\right) \left(7\right)$
$= - 104 + 35$
$= - 69$