Explanation

(b)
Given, $f(x) = 3|2 + x|$
$f(x) = \left\{ \begin{matrix}
3(2 + x), & x \geq - 2 \\
- 3(2 + x), & x \leq - 2
\end{matrix} \right.\$
On differentiating w. r. t, $x$, we get
$f^{'}(x) = \left\{ \begin{matrix}
3, & x \geq 2 \\
- 3, & x \leq - 2
\end{matrix} \right.\$
at $x = - 3,f^{'}(3) = - 3$