Use the following data

Question

2C(s) + 4H2(g) --> C3H8(g)
DH= -103.85 kJ/molrxn

C(s) + O2(g) --> CO2(g)
DH= -393.51 kJ/molrxn

H2(g) + 1/2O2(g) --> H2O(g)
DH= -241.82 kJ/molrxn

to calculate the heat of combustion of propane, C3H8

C3H8(g) + 5O2(g) --3CO2(g) + 4H20(g)

Answer 1

You have a typo in #1, that should be 3C(s).

Reverse #1, add to 3x #2, and to 4x #3.