1. Is it possible to draw four lines on a plane and mark seven points on them so that there are exactly three marked points on each line?
Answer: possible

Instructions. Example 1. Among the four lines, there are two parallel ones. The other two intersect them at different points and intersect each other. We mark five points of intersection of the lines and one more point on each of the parallel lines. Seven points are marked, and there are three marked points on each line.

Example 2. Three lines pass through one point, and the fourth intersects each of them. Four points of intersection are marked and one more point on each of the three lines passing through one point. Seven points are marked, and there are three marked points on each line.

Example 3. If every two lines intersect (6 points of intersection). Five points of intersection are marked and one point on each line passing through the unmarked point of intersection.

Criteria. Any natural number of correct examples: 7 points