Sally takes two bar magnets and randomly tapes one end of each bar magnet. she labels the magnets a and b. she brings the taped ends of two magnets together and they attract each other. sally knows that opposite poles of magnets attract. she then brings the taped end of a third magnet (magnet c) near each of the first two magnets. predict her observations.

I already answered this quesiton. The fact is that there are only two kind of poles and since the two taped poles of the magnets labeled A and B attracts one to each other, we know that the two taped poles of the first two magnets are oppsosite.

Then, the taped pole of the third magnet has to be equal to one of the first two taped poles and opposite to the other of the first two taped poles.

That drives you to conclude (predict)  that when she brings the taped end of the third magnet (magnet C) near each of the first two magntes, in one case they will attract each other and in the other case they will repele mutually.