Uranium-235 and uranium-238 are considered isotopes of one another

Indeed they are. The uranium atoms have separate numbers of neutrons in their nuclei, but still have the same number of protons.

Since there is the same amount of agn03 in both silver chloride and silver nitrate they produce the same amount of moles. therefore silver chloride produces the same amount of silver nitrate, so your answer is 15.0 moles of silver nitrate. i hope this !