Pl help me in learning to find out enthalpy of formation (HESS'S LAW).

Solve the ques below in detail and explain it so that i can learn from it.

rate assured!!!!!!  thanx.

 

Q-Cal. enthalpy of formation of ethyl alcohol from following data==

 

1) C₂H₅OH + 3O₂     2CO_2(g)  + 3H₂O   ( H= -1368 KJ)

 

2) C(s) + O₂(g)    CO₂(g)    ( H= -393.5 KJ) 

 

3) H₂  +  1/2O₂     H₂O   ( H= -286.0 KJ)