Express the following vector equation as a system of linear equations.

$$x_1 \left[\begin{matrix} 2 \cr 1 \cr \end{matrix}\right]+ x_2 \left[\begin{matrix} 5 \cr 9 \cr \end{matrix}\right]= \left[\begin{matrix} 2 \cr -2 \cr \end{matrix}\right]$$

(Keep the equations in order.)
$x_1 +$ $x_2 =$ .

$x_1 +$ $x_2 =$ .