Hydrogen azide, HN3, decomposes on heating by the following unbalanced reaction: HN3(g) N2(g) + H2(g) If

Question:

Hydrogen azide, HN3, decomposes on heating by the following unbalanced reaction:
HN3(g) → N2(g) + H2(g)
If 3.0 atm of pure HN3(g) is decomposed initially, what is the final total pressure in the reaction container? What are the partial pressures of nitrogen and hydrogen gas? Assume the volume and temperature of the reaction container are constant.