Answer:
remember, the number of atoms is represented by the subscript. if there is a coefficient, multiply it by the subscript. if there is no subscript or coefficient written, assume it is 1.
cu = 1 atom on the reactants side, 1 atom on the products side
s = 1 atom on the reactants side, 1 atom on the products side
O = 2 atoms on the reactants side, 2 atoms on the products side