I have been really struggling with this second. But! I figured out in the last lesson (and then applied it to this one) that I have been attacking the wrong part of the argument. So maybe this will help anyone who has been struggling. I have been trying to attack the conclusion and make it invalid. However, I realized that that was not the point. The point is to attack the argument as a whole. So, in other words, attack the system of support. Attack assumptions in the premises; do not attack the conclusions themselves. It sounds simple, but it really did just change the way I was going about answering these questions. I hope this helps someone else who is struggling!