Without any pictures, it is hard to assign a particular value. Assuming that all three coins are well circulated, the 1879 and 1900 are common Morgans and would only be worth melt or a bit more. My Local Coin dealer pays $22 for them and sells them for $25. Melt is around $18 or so. The 1899 has a little bit of value to it even in circulated condition and would probably be worth about $50-100 depending on condition. The Grey Sheet has it listed around $135 in VG condition. Numismaster has it listed for $123 in VG condition. A shady dealer may only want to pay you melt but it is definitely worth more than that. If you post pics, a more accurate price can be given.