text: This is really a chemistry question, not a Physics question.\n\nCO2 is one C and two 0, so 6CO2 is 6 C and 12 O\nH2O is 2 H and one O so 6H2O is 12 H and 6 O\nThe total is 6 Carbon atoms, 12 Hydrogen atoms and 18 Oxygen atoms.\n\nC6H12O6 is 6 C, 12 H and 6 O\nO2 is 2 O, so 6O2 is 12 O\nThe total is 6 Carbon atoms, 12 Hydrogen atoms and 18 Oxygen atoms.\n\nSince both sides are the same the equations is balanced.