Acetylene is CHCH (triple bonded), Nitrous oxide is N2O. The reaction would be:
CHCH + 5 N2O ----> 2 CO2 + H2O + 5 N2
People burn things with nitrous oxide because it actually has a higher percentage of oxygen present than natural air. The oxidation reaction is the same though... oxygen adds to the fuel (in this case aceylene) to form CO2 and H2O.
This is a simplified picture, because in true combustion, there are alot of side products.