HEss's law help!?

Question

I can't solve this problem. Can someone show me how to get this and show me the work?

2O3(g) --> 3O2(g) Delta H= -427 kJ
O2(g) ---> 2O(g) Delta H= 495 kJ
NO (g) +O3(g) --> NO2(g) + O2(g) Delta H= -199 kJ

What is the delta H for the reaction
NO(g) + O (g) --> NO2(g)

Answer 1

Flip 1st equation and halve
(3/2)O2-->O3 213.5kj

Flip 2nd equation and halve
O -->(1/2)O2 -247.5kj

Leave the 3rd as is
NO + O3 -->NO2 + O2 -199kj

The O3 and O2 all cancel so we have
NO + O --> NO2
and Delta H is found by just straight adding the resulting energies