Answer
$y=-1$
Work Step by Step
In order to determine $y$, we have to compute the determinants $D,D_y$:
$D=\begin{vmatrix}1&-2&1\\2&1&-1\\3&2&-2\end{vmatrix}=-2+6+4-3+2-8=-1$
$D_y=\begin{vmatrix}1&7&1\\2&0&-1\\3&-2&-2\end{vmatrix}=0-21-4-0-2+28=1$
We use Cramer's Rule to determine $y$:
$y=\dfrac{D_y}{D}=\dfrac{1}{-1}=-1$
