PLEASE HELP I NEED THIS DONE IN LESS THEN 2 HOURS!!! ILL GIVE BRAINLIST PLEASE HELP <3

The law of conservation of matter states that matter can be neither created nor destroyed. Your friend shows you the following chemical equation:
CaCO3 -> CaO + CO2

He says that because the oxygen atoms are split between two different molecules in the products, the equation does not support the law of conservation of matter. Is your friend right? Explain your answer. Draw a model showing the number of each type of atom in the reactants and products. Use your model to explain your answer.