Now use the average value of Kb the base dissociation constant of acetate anion to calculate an average value for Ka, the acid dissociation constant of acetic acid.

Kb: 1.33x10^-10

1 answer

I take it that 1.33E-10 is the average of Kb for acetic acid and you want to calculate Ka.
Ka*Kb = Kw = 1E-14
You know Kw and Kb, solve for Ka.