How to determine the number of moles in the following?

Number of moles = (Mass in g) / (Molar mass in g/mol)

(a)
Molar mass of Ag = 107.9 g/mol
Number of moles of 2.37 g Ag = (2.37 g) / (107.9 g/mol) = 0.0220 mol

(b)
Molar mass of S = 32.06 g/mol
Number of moles of 616.9 g S = (616.9 g) / (32.06 g/mol) = 19.24 mol

(c)
Molar mass of Zn = 65.38 g/mol
Number of moles of 172 g Zn = (172 g) / (65.38 g/mol) = 2.63 mol

(d)
Molar mass of Fe = 55.85 g/mol
Number of moles of 1.43 kg Fe = (1.43 × 1000 g) / (55.85 g/mol) = 25.6 mol

molecular weight of each element as stated in the periodic table in g/gmole, so you take the mwt and divide your elements mass by its mwt.

For each element, you need to look up the mass of 1 mole. Then compare that to the mass in the problem.
For example: Silicon Si, has an atomic mass of 28.0855 grams per mole. So if you have 14.0428 grams, that is 0.50000 moles.