Answer: { } or empty set.
Explanation:
We are given two lines on the graph.
Line l and line m.
Lines l and m are parallel to each other.
Parallel lines never intersect each other at any point.
Note: Solution of a system or a set of lines on the graph are the point(s) where lines intersect each other.
As we know parallel lines would not intersect each other at any point, there would not be any solution of the system.
So, the solution set would be { } or empty set.