If I had a valid argument in the form of premises p1, p2, ... pn, q and conclusion r, then could I show that the argument form with premises p1, p2, ... pn and conclusion q --> r is valid? I'm not sure I see why the former argument being valid ensures that the latter argument is valid.
And if I had the argument form with premises (p and t) --> (r or s), q --> (u and t), u --> p, not s, and conclusion q --> r, how could I apply the stuff above to show that this one is valid?