Consider the equilibrium:
3A <----> B
You prepare a mixture with initial concentrations [A]0 = 0.61 mol/L, and [B]0 = 0. You wait until the mixture reaches equilibrium, and then you measure the concentration of B: [B]eq = 0.11 mol/L. From your experiment compute the equilibrium constant Kc of the reaction.
You can use a table to analyze this problem.
3A ----------> B
Initial Conc 0.61 ...
This solution provides calculations and explanations for computing equilibrium constants of a reaction.