Answer:
2C8H18 + 25O2 -> 16CO2 + 18H2O
(16C, 36H, 50O)
H2O requires 2H per H2O, Meaning that you'd have 9H2O's from 1C8H18, but you still need that O2 for the CO2 and because the reactant side has 8C (within C8H18) You'd have to times the amount of required O2 from CO2 by 8. Even then you still don't have enough for both CO2 and H2O so you'll have to multiply MORE causing a bigger chain reaction resulting in 2C8H18 + 25O2 -> 16CO2 + 18H2O