1. Substitute y=-x+2 into x-3y=-18:
x-3(-x+2)=-18,
x+3x-6=-18,
x+3x=-18+6,
4x=-12,
x=-3.
Then y=-(-3)+2=3+2=5.
2. The graphs of two equations you can see in attached diagram. Common point (the point of intersection) represents the solution of the system of two equations.
Answer: (-3,5) or x=-3, y=5.
