Write the system of linear equations in the form $Ax=b$ and solve this matrix equation for $x.$

$-2x_1-3x_2=7$

$6x_1+x_2=-45$

$[]\left[\begin{array}{c}{x}_1\end{array}\right]$

$x_2=\left[\begin{array}{c}7\end{array}\right]$

$-45$

$\left[\begin{array}{c}{x}_1\end{array}\right]$

$x_2=[,]$