The description does not say that heptagon has to be convex, i.e. all of its interior angles need not be less than 180^°. Since (2 x 7 - 4) ×90 = 900, the interior angles of all heptagons total 900^°. The creation of a heptagon with all the given conditions is possible as the diagram shows. Notice that four of the interior angles are acute and the other three are reflex angles.