Answer
$|V|=\sqrt{73}.$
Work Step by Step
The magnitude of a vector is given by the possible square root of the sum of the squares of its horizontal and vertical components.
Let $V=\langle -8,-3\rangle.$
Then \begin{align*}
|V|&=\sqrt{(-8)^{2}+(-3)^{2}}\\
&=\sqrt{64+9}\\
&=\sqrt{73}.
\end{align*}
Hence, $|V|=\sqrt{73}.$