For Li+,
Protons= The atomic number, Which is 3
Neutrons= Atomic mass - atomic number. (7-3=4) Which is 4.
Since this element is a positive charge, to find the number of electrons you need to subtract 1 from the number of protons. (3-1=2) Your answer is 2
3 Protons, 4 Neutrons, 2 Electrons :)