Answer
$\begin{bmatrix}
12 \\
-3
\end{bmatrix}$
Work Step by Step
We are given:
$v_1=(1,-1)\\
v_2=(2,1)$
Then,
$A(3v_1-v_2)=3(Av_1)-(Av_2)\\
=3(2v_1)-(-3v_2)\\
=6v_1+3v_2\\
=6\begin{bmatrix}
1 \\
-1
\end{bmatrix}+3\begin{bmatrix}
2 \\
1
\end{bmatrix}\\
=\begin{bmatrix}
12 \\
-3
\end{bmatrix}$
