I believe I could work this problem fine had the instructor not placed statements #3,4, and 6, as well as the reasons # 5 and 7. I can't seem to understand where he's using the transitive property in #5. If these steps weren't here I would assume, I'm only using substitution to prove that "RS" = "RU" and therefore satisfies, along with the parallelogram statement, that this quadrilateral or parallelogram is indeed a rhombus. Coming from the statement of a parallelogram and knowing the congruency of two of the adjacent sides, I just don't understand why there's any need for a transitive property. Does any one have any ideas or a direction they can lead me in?