To balance a combustion reaction, you usually balance the C, then the H, and then the O after assuming the H,C,O fuel has a 1 stoichiometric coefficient. Half of the time, you will have n/2 in front of the O2 which I think is preferable as it corresponds to the appropriate equation per mole of fuel (Enthalpy will be the molar heat of combustion), but most books and standardized tests require integer stoichiometry - just multiply all terms by 2.
C15H30 + 45/2 O2 → 15CO2 + 15H2O
Now, it's just a stoichiometry problem going from extensive to extensive variable. Cancel units to get where you want to go and put in the appropriate conversions and information to get there:
1 mole fuel (15 mole W / 1 mole fuel) (18 g W/mole W) (1 ml /1 g W) (1 liter/1000 ml) = liters of water.