Can you solve this reverse geometry problem?
I am sure you all know how to plot points on a grid. How about going in the other direction. You are given two points on a circular piece of paper along with their coordinates. The x coordinates of the two points are different and so are the y coordinates. The scaling is the same for both x and y. Using a ruler (not just a straightedge), a compass and, if necessary, a protractor, can you draw the coordinate axes?
I think this would make a good problem for a geometry class. The problem requires no knowledge of either Euclidean geometry or algebra.