A substance's solubility product, Ksp, is the mathematical product of its dissolved ion concentrations raised to the power of their stoichiometric coefficients. The dissociation equation of the generic metal hydroxide would be as follows:
M(OH)2 = M2+ + 2OH-
We calculate solubility as follows:
7.85×10^−18 = [M2+] [OH]^2
7.85×10^−18 = [x] [2x]^2
7.85×10^−18 = 2x^3
x = 1.58 x 10^-6 M
Hope this answers the question. Have a nice day.
