hat is the mass number of the xenon isotope with   neutrons?

It seems like there's a mistake in your question. You didn't mention the number of neutrons for the Xenon isotope. The mass number of an isotope is calculated by adding the number of protons and neutrons. Xenon (Xe) has 54 protons. So, if you provide the number of neutrons, we can add that to 54 to get the mass number of the Xenon isotope.