You may use any theorems that have been discussed in class. There are many proofs. Then use 8.15 enough times to get univ. Assume left side. Use the standard method to get each universal as a temp.
R are temp.
R is a temp. There are undoubtedly many other correct proofs, and the students found even more incorrect ones. One of the two wffs B , C below is a theorem with a very short and simple proof, and the other is not even a valid formula. Do nothing with the other wff. Again, there are MANY proofs.