Answer
(a) $A+B$ not defined.
(b) $A-B$ not defined.
(c) \begin{align*}
2A&=2\left[\begin{array}{r}{3} \\ {2} \\ {-1}\end{array}\right]=\left[\begin{array}{r}{6} \\ {4} \\ {-2} \end{array}\right].
\end{align*}
(d)$2A-B$ not defined.
(e) $\frac{1}{2}A+B$ not defined.
Work Step by Step
Given $$
A=\left[\begin{array}{r}{3} \\ {2} \\ {-1}\end{array}\right], \quad B=\left[\begin{array}{ccc}{-4} & {6} & {2}\end{array}\right]
$$
(a) $A+B$ not defined.
(b) $A-B$ not defined.
(c) \begin{align*}
2A&=2\left[\begin{array}{r}{3} \\ {2} \\ {-1}\end{array}\right]=\left[\begin{array}{r}{6} \\ {4} \\ {-2} \end{array}\right].
\end{align*}
(d)$2A-B$ not defined.
(e) $\frac{1}{2}A+B$ not defined.