I have a quiz tomorrow and I need to figure out how to solve a linear equation using a graph ASAP. Can you please help me?

SOLUTION
The given equations are
[tex]\begin{gathered} x+y=18 \\ y=x+12 \end{gathered}[/tex]The graph of the equations are shown:
Notice that the line intersect at (3,15)
Therefore, the solutions of the system of equations are
[tex]x=3,y=15[/tex]