Let there be a finite number of straight lines in the plane, none of which are three in one point to cut. Show that the intersections of these straight lines can be colored with 3 colors so that that no two points of the same color are adjacent on any of the straight lines. (Two points of intersection are called adjacent if they both lie on one of the finitely many straight lines and there is no other such intersection on their connecting line.) combinatoricsColoringlines