The number of protons, neutrons and electrons, respectively, in 115Cd2+ are?

Answer 1

Look up the atomic number of Cd (from the periodic table). That is the number of protons.
#protons + #neutrons = mass number(115)
# electrons = # protons in a neutral atom. This atom is not neutral and since the charge is +2 it must have two fewer electrons than protons. You can take it from here.