How would a line graph look like depicting a spurious relationship between X and Y, controlling for Z.

The vertical axis will show the percentage favoring the legalization of marijuana.

Invent plausible percentages for the values of Y.

The horizontal axis will show the two values of age, "younger" and "older." There will be two lines inside the graph: one for "low" education and one for "high" education.

I am not quite sure where to start on this!