Answer:
C6H12O6 + 6O2 → 6CO2 + 6H2O
From the equation, we can see that 1 mole of C6H12O6 reacts with 6 moles of O2. Therefore, if we have 303 moles of C6H12O6, we need 6 times as many moles of O2:
303 moles C6H12O6 × 6 moles O2 / 1 mole C6H12O6 = 1818 moles O2
So we have 1818 moles of oxygen.