ILL 1969 Problem 68
Given points in the plane, no three of which are collinear, prove that we can choose points among them that form a convex quadrilateral.
Dataset text AoPS wiki problems. Quoted with source.
Solutions
No solution is on olymmath yet. Official and human solutions come first when they arrive. AI solutions come after them, with a label.
Similar problems
These problems have the most words in common with this statement.