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Given the standard enthalpy changes for the following two reactions:

$(1)N_2(g)+2O_2(g)N_2{O}_4(g),H=9\mathrm{.}2kJ$

$(2)2N_{2}O(g)2N_2(g)+O_2(g),H=-164\mathrm{.}2kJ$

What is the standard enthalpy change for the following reaction?

$(3)2N_{2}O(g)+3O_2(g)2N_2{O}_4(g),H=$

Standard enthalpy change $=kJ$