1) What is the atomic mass of oxygen, and what units is it in? From there you should be able to convert grams to moles.
2) Look at mole ratios. How many moles of H2O are produced per mole of O2? After getting moles, you can again use atomic mass (this time of H2O of course) to calculate grams.
3) Same thing as steps 1 and 2.
4) Calculate how much CO2 will be produced by 6.81 grams C5H10 in a 100% reaction (100% reaction means that at the end, there is no remaining C5H10 or O2 remaining as all has reacted) and compare it to the given 19.2 grams.