-0.04 = -0.0591/2 × log(0.24 / x)
You can divide -0.592/2 to get it as a whole number
-0.04 = -0.02955× log(0.24 / x)
Divide each side by -0.02955
1.354 = log (0.24 / x)
Use antilog (10^)
22.6x = 0.24
Solve for x algebraically now
x = 1.062×10^-2
Therefore
[Cd^2+] = 1.062×10^-2 mol / L
Hope...