Calculate the number of neutrons in an atom of an element that has a mass number of 98 and an atomic number of 42

There are 56 neutrons. To find them, you just have to subtract the atomic number with the atomic mass. If you dont know, the atomic number is the number of protons (and electrons) in an atom. The atomic mass is the number of both the protons and neutrons. Of you subtract the atomic number, you get protons.