[uchiness]

i know that this definetly would be in the exam, would anyone be able to show me a step by step way of working out the answers please. (thanks in regards)

[esf.edu]

Here is an outline of the procedure for part a, which is a pretty standard Hess's Law problem. 
i) write the reaction for CH₄ combustion
ii) write the reverse reaction of CH₄ combustion and the corresponding reaction enthalpy
iii)  add up the reaction in (ii) and the two reactions given in the problem statement(or multiples thereof) in such a way as the final reaction is CH4 synthesis from the elements.  Add the enthalpies of the reactions (paying attention to the sign of the reaction enthalpy in i) in the same way to get the enthalpy of reaction CH4 synthesis from the elements.
iv)  The definition of the enthalpy of formation and your answer to (ii) gives you the answer to the problem.


For part b: write the reaction for atomization and add up the number and type of bonds that are broken.  Then apply Hess's Law.