[tex]\left\{\begin{array}{ccc}x=3y+9&\text{substitute it to the second equation}\\9-x=-3y\end{array}\right\\\\9-(3y+9)=-3y\\\\9-3y-9=-3y\qquad\text{add 3y to both sides}\\\\9-9=0\\\\0=0\qquad\mathbb{TRUE}\\\\Answer:\ \boxed{infinite\ solutions}[/tex]
