x=-1, y=7
1) Since we have the following system of linear equations, by the Method of Substitution
y=2x +9
y=6-x
Rewriting those
y=2x +9
y= -x + 6 Multiply by 2
2) Now we can add those, elimination the x variables:
6-x= 2x +9
-3x =9-6
-3x =3
x=-1
3) Let's plug into one of those equations, y=6-x
y=6-(-1) y =7