state and explain how the concentration of nitrogen gas would be affected by an increase in pressure

Answer 1

Depends upon the reaction doesn't it? What's the reaction?

Answer 2

the reaction is:
2NO yield N2 + O2

Answer 3

An increase in pressure will not affect the equilibrium. Pressure shifts the equilibrium to the side with the few mols. In this case both sides have 2 mols gas; therefore, the reaction will be unchanged.