[seong8737]

2 NH3OH(+) --> N2O

2 NH3OH(+) --> N2O + H2O

2 NH3OH(+) --> N2O + H2O + 6 H(+)

2 NH3OH(+) --> N2O + H2O + 6 H(+) + 4 e-

then combined with 4 Fe(3+) + 4 e- --> 4 Fe(2+) will result in your reaction equation.

Maybe the H(+) is a catalist in the reaction.

Ok.... I have found my answer.