[JustinCh3m]

Are you aware of the "I.C.E. Method" for such problems, and the difference between Q and K (or in this case, Kp)?

Look up "solving equilibrium problems" (or something similar) in your textbook's index (or skim the chapters' contents area of your textbook).  This topic is usually covered at the beginning of the second semester of G-chem, usually right after Kinetics.