* CO2 (Carbon Dioxide): Each CO2 molecule has 2 oxygen atoms.

* H2O (Water): Each H2O molecule has 1 oxygen atom.

Calculations:

* Oxygen atoms in CO2: 3 CO2 molecules * 2 oxygen atoms/CO2 molecule = 6 oxygen atoms

* Oxygen atoms in H2O: 4 H2O molecules * 1 oxygen atom/H2O molecule = 4 oxygen atoms

Total: 6 oxygen atoms + 4 oxygen atoms = 10 oxygen atoms

Therefore, there are 10 oxygen atoms in 3CO2 4H2O.