how many grams of propane would be burned with 80.0g of oxygen?

C3H8 + 5O2 ==> 3CO2 + 4H2O

mols o2 = grams/molar mass = ?
Using the coefficients in the balanced equation, convert mols O2 to mols propane.
Then convert mols propane to grams. g = mols x molar mass = ?