A) State Hess's Law $\Delta$ H $\degree$ Data Given Below to Calculate $\Delta$

A) State Hess's Law.
B) Use the $\Delta$ H $\degree$
data given below to calculate $\Delta$ H $\degree$
or the reaction:
C₂H₄(g) + H₂(g) $\rightarrow$ C₂H₆(g)