On a normal two dimensional x-y graph in which two equations are represented, each involving y and x and no other variables, the intersection of the graphs of the equations represent the solution(s). If the two graphs are linear, the solution (x,y) is the single point where the straight lines intersect. If the lines are parallel, there is no solution.
The graphs do not need to be linear, but if the graphs do not intersect there is no solution.
Accurate drawing of the graphs is essential if an accurate solution is required. To check the solution or solutions, get the x coord(s) of the intersection point(s) and work out the corresponding y value(s) for each equation. They should match the y coord(s) of the intersection points.
If you can, you should solve the system of equations using a different method to confirm the graphical result.