Or equivalently, "3 dots on boundary of convex hull vs. not so". - Leo Crabbe, Aug 01 2020
Dots can be connected to create one triangle within another vs. not so.
Dots can be connected to create one triangle within another vs. they can't be
Dots can be connected to create two triangles within each other vs. they can't be
Cameron Fetter
See BP889 for version with nesting disallowed.
Bongard Problems with world non-intersecting triangle and circle outlines, nesting allowed vs. other Bongard Problems
Aaron David Fairbanks