In this problem ,we are given with the solubility constant of nickel dichromate which when dissolved in ammonia results to dichromate ion and nickel ion. In this case, with the given initial concentration 0.06 M, the equation becomes. 4x10^-10 = x^2/ (0.06-x) where c is the final concentration of NH3. x is equal to 4.89 x 10^-6 M.