How to Solve  an Equilibrium Problem : General Approach

Step 1.  Set up a table of concentrations:
            Initial concentrations, Change in concentrations (x) , Final concentrations.

Step 2.  Write down an equilibrium constant (K) expression for the reaction.

Step 3.  Substitute equilibrium concentrations into the equilibrium constant (K) expression:
 
Step 4.  Solve the  equilibrium constant equation for the unknown (x) with all hooks and crooks.