Mass Number quantifies the number of protons and neutrons in the atom. Electrons are so small that they do not even matter in the calculation. Protons and Neutrons are approximately 1 A. Atomic Number refers to where the atom is on the periodic table, such as Hydrogen being Atomic Number 1, but also quantifies the number of protons. In your situation the atomic number is 32 meaning it is Germanium but also meaning it has 32 protons. When we add the number of protons and number of neutrons to find the mass number we do 32 (protons) + 31 (neutrons) to get a total mass number of 63. 63 is your answer.