Answer: You would add a 6 to the coefficient of CO2 and H2O on the right and O2 on the left to balance the formula.
Explanation:
carbon- 1 on the right, 6 on the left
Oxygen- 3 on the right, 8 on the left
Hydrogen- 2 on the right, 12 on the left
When a 6 is added as a coefficient, all of the elements are the same on each side of the formula, making it balance.