what is the delta-H of reaction for: [N2(g) + O2(g) = 2NO(g)] if..?

Question

[4NH3(g) + 5O2(g) = 4NO(g) + 6H2O delta-H of reaction = -1170 kJ] and [4NH3(g) + 3O2(g) = 2N2(g) + 6H2O delta-H of reaction = -1530 kJ]

Answer 1

2 N2 (g) + 2 O2 (g) = 4 NO (g) from subtraction, give a change in H (enthalpy) as (1530 - 1170)/2 = 360/2 = 180 kJ