We are given ab ∥ de. Because the lines are parallel and segment cb crosses both lines, we can consider segment cb a transversal of the parallel lines. Angles ced and cba are corresponding angles of transversal cb and are therefore congruent, so ∠ced ≅ ∠cba. We can state ∠c ≅ ∠c using the reflexive property. Therefore, △acb ~ △dce by the.