Answer:
it is alredy balanced
Step-by-step explanation:
CaCO3 -------> CaO + CO2
In the reactant side In the product side
Ca = 1 atom Ca = 1 atom
C = 1 atom C = 1 atom
O = 3 atom O = 1+2 = 3 atom
so there is no need to balance it cause it is already balanced.