Answer:
pH  = 13.09
Explanation:
Zn(OH)2 --> Zn+2 + 2OH-   Ksp = 3X10^-15
Zn+2 + 4OH-   --> Zn(OH)4-2   Kf = 2X10^15
K = Ksp X Kf 
   = 3*2*10^-15 * 10^15 
   = 6
Concentration of OH⁻ = 2[Ba(OH)₂] = 2 * 0.15 = 3 M
                 Zn(OH)₂ + 2OH⁻(aq)  --> Zn(OH)₄²⁻(aq)
Initial:           0             0.3                      0
Change:                      -2x                     +x
Equilibrium:               0.3 - 2x                 x
K = Zn(OH)₄²⁻/[OH⁻]²
6 = x/(0.3 - 2x)²  
6 = x/(0.3 -2x)(0.3 -2x)
6(0.09 -1.2x + 4x²) = x
0.54 - 7.2x + 24x² = x
 24x² - 8.2x + 0.54 = 0
Upon solving as quadratic equation, we obtain;
x = 0.089 
Therefore,
Concentration of (OH⁻) = 0.3 - 2x 
                                     = 0.3 -(2*0.089)
                                   = 0.122
pOH = -log[OH⁻] 
          = -log 0.122
           = 0.91
pH = 14-0.91 
      = 13.09
 
        
             
        
        
        
Lithium Oxide
I just search it up to be honest