Some of that 1970's tile was put up with a wire mesh and cement! They really meant for it to stay a long time. Still, it can come down with a little effort but you may have to hang new sheetrock where you remove the tile. Best results would be to use the tile glaze sold at most home improvement stores.
It seems you may want to know the answer to this question because you are concerned that the home has been on the market for one year and has not sold or had any offers and you are wondering what is wrong with the house. If that is the case, you may want your buyers agent to research average days on the market for comparable homes. It would not be surprising to find a home in my market area on MLS for one year with no offers. Also, even if you could find out what a seller agreed to take six months ago that does not mean he will take the same number today. Lots of things could have changed since then to affect the number that seller will be happy netting at closing. If you like the home, have your buyers agent give you some guidance as to an offer and go for it! Keep in mind, the seller in most states have an obligation to disclose to potential buyers know defects with the home.