IMO Shortlist 2015 problem G7
Dodao/la: arhiva30. kolovoza 2018.
Let be a convex quadrilateral, and let , , , and be points on the sides , , , and , respectively. Let the line segment and meet at . Suppose that each of the quadrilaterals , , , and has an incircle. Prove that the lines , , and are either concurrent or parallel to each other.