Answer
$\{(9,-3)\}$
Work Step by Step
Graph each line
(plot two points per line, such as the interceptcs)
$x+y=6:\quad \left[\begin{array}{lll}
x=0 & ... & y=0\\
y=6 & & x=6\\
(0,6) & & (6,0)
\end{array}\right]$
$ y=-3\quad$.... horizontal line through $(0,-3)$
There is an intersection point,
the solution set is $\{(9,-3)\}$
