Strontium hydroxide or SrOH_2 is a strong base and will completely ionize. This means that virtually all SrOH_2 will dissociate in water into metal cations and hydroxide ions.
"Sr"("OH")_2(s) -> "Sr"^{2+}+2"OH"^-
pOH is the negative log of the concentration of hydroxide molecules. Since we know that SrOH_2 will completely ionize in solution, we can use the given concentration to solve for pOH.
pOH = -log [OH^-]
pOH = -log [2.0 * 10^-1 M]
pOH = 0.70
The question asks for pH and not pOH. Using the formula below, we can solve for pH.
pH + pOH = 14
pH + 0.70 = 14
pH = 14-0.70 = 13.3
pH = 13.3
The pH is 13.3 at "25 degrees Celsius"