Final answer:
The shapes have a common number of sides. They are all triangles.
Step-by-step explanation:
The shapes in the given images share a common number of sides. Specifically, the shapes all have three sides, which makes them triangles. To draw two more shapes that belong to the same set, you can create two more triangles with different sizes or orientations. Here are the two additional shapes:
Shape 1: A triangle with sides of length 4 cm, 5 cm, and 6 cm.
Shape 2: An equilateral triangle with all sides of length 7 cm.