To determine the concentration of hydroxide ions (OH-) in a solution of a given compound, you need to consider the dissociation of the compound in water. In the case of CH3COONa, it dissociates into acetate ions (CH3COO-) and sodium ions (Na+).
Since acetate ions are a weak base, they hardly react with water to produce hydroxide ions. Therefore, we can assume that the contribution of hydroxide ions from the dissociation of CH3COONa is negligible. Hence, the OH- concentration in a 0.08 M solution of CH3COONa is approximately 0 M.
If you want to determine the OH- concentration in a solution, it would be more relevant to consider compounds that are strong bases, such as sodium hydroxide (NaOH), potassium hydroxide (KOH), etc.