Answer:
The graph of such system of equations should show two lines with different slopes, and therefore intersecting in one unique point.
Explanation:
In order to have a system of linear equations in two variables give as answer only one solution (that is a unique point on the plane), the graph of such equations should be two lines with different slopes, and therefore intersecting in one unique point.
Graphs with parallel lines will not be correct since there is no intersection, and therefore no answer to such systems.
Graphs that show lines that overlap are not an answer either, since in such case there are infinite number of solutions (all the points on each line)