Homework(calc enthalpies)

[sarahtang4B]

On homework 4D15 how do we know we have to write the balanced equations whereas on 4D17, why don't we have to write the equations?
Also, how do we write the balanced equations?

[EllerySchlingmann1E]

for #15, because you were given the standard combustion enthalpies, the question is asking you to write out the chemical equations for the combustions of the reactants and products and use Hess' Law to determine the overall reaction enthalpy. Whereas, for #17, we can use the standard enthalpies of formation for the reactants and products to find the standard reaction enthalpy.