Given the following data:
2o3 -> 3o2 (enthalpy = -427 kj)
o2 -> 2o (enthalpy = +495 kj)
no + o3 -> no2 + o2 (enthalpy = -199 kj)

calculate the enthalpy for the reaction
no + o -> no2 using hess's law.

Just try to find how you will get the reaction by adding the other reactions. Reverse the second eq as O is in reactant side and half it..

Now in the final reaction there is neither ozone nor oxygen so now you have oxygen on the products side after adding reversed

 2 and 3, O ->1/2 O2 

adding this to the third eq you get, 

NO+O +O3 -> NO2 +3/2 O2

 Now you need to remove O3 and O2 using the first equation, 

So reverse the first one,half it and add, 3/2O2-> O3 adding it removes O3 and O2 you get the requires equation,

 NO + O->NO2 you can do the calculation bit yourself when you add reactions Enthalpy is also added by Hess law so yeah that part should be pretty simple.