Given that we assume that all the bases of the triangles are parallel.
We can use AAA or Angle-Angle-Angle to prove that these triangles are similar.
Each parallel line creates the same angle when intersecting with the same side. For example: The bases of each triangle cross the left side of all the triangle. Each angle made by the intersecting of the the parallel base and the side are the same. Thus, each corresponding angle of all the triangles are congruent. If these angles are congruent, then we have similar triangles.
