The solubility product would be written as follows:
Ksp = [M][3X]^3
letting s as the molar solubility
Ksp = s(3s)^3
Ksp = s(27s^3)
Ksp = 27s^4
The solubility product is a mathematical product of the dissociated ion concentration in the solution and raised to the power of the stoichiometric coefficients. Hope this helps.
