if we had two linear equations and graph them, the solution to the system, namely the values for "x" and "y" that make both equations simultaneously true, happens where both graphs intersect, or cross each other.
now, in this picture above, the assumption is that line M is right on top of line N, so they're both pancaked on top of each other, so they're really intersecting each other all the way to infinity, and since lines to go infinity, then they have infinitely many solutions.
