How can I find how many atoms of C, Ca and O there are in 0.3g of chalk, knowing that chalk is 100% CaCOsub3?

Please Help, I really don't understand :(

How can I find how many atoms of C, Ca and O there are in 0.3g of chalk, knowing that chalk is 100% CaCOsub3?
1. First of all calculate the mole number of CaCO3 contained in 0.3-g. Consider that MW of CaCO3 is 100-g/mol.





2. Using Avogadro's number of molecules/mol, calculate how many molecules you have in 0.3-g. Consider 6.023(10)23 molecules/mol.





3. Multiply that number per the amount of atoms represented in CaCO3 formulae:





1. 0.03-mol CaCO3 contained in 0.3-g of CaCO3


2. 1.8069(10)21-molecules of CaCO3 contained in 0.03-mol CaCO3


3.





Ca = 1 X 1.8069(10)21 atoms


C = 1 X 1.8069(10)21 atoms


O = 3 X 1.8069(10)21 atoms = 5.4207(10)21 atoms