Help please it's due in 20 minutes and I can't find the answers;-; help

according to this reaction:

by using the ICE table:

              CO(OH)2 → CO2+  +  2OH-

intial                                0             0

change                           +X           +2X

Equ                                   X              2X

when Ksp = [CO2][OH-]^2

by substitution:

3.6 x 10^-16 = X * (2X)^2

3.6 x 10^-16 = 4 X^3

∴X = 3.88 x 10^-6 M