See attached and directions.
For the Hess' Law calculation:
Eqs #1 to 3 are enthalpies of formation. The enthalpy of any reaction is given by:
DH = DHf (products) - DHf (reactants). Remember to halve the DH value for SO3, because the one given is for formation of 2 moles of SO3.
I get an answer of between -400 and ...
The answers are given with short explanations.