A = mass number which is equal to the total number of protons + number of neutrons, Z= atomic number of any element which is also indicates Number of protons or number of electron in the given atom.
The formula to calculate neutron would be :
mass number - proton
31 - 15 = 16
Thus 16 neutrons are found in one atom of P
There are 4 atom in one molecule
Thus
4 atom /1 molecule 9 molecule 16 neutron / 1 atom
= 4916= 576 neutrons
