Изменения

{P}(A \mid B_1) = \genfrac{}{}{}{0}{23}{7} ,~ {P}(A \mid B_2) = \genfrac{}{}{}{0}{32}{7} ,~ {P}(A \mid B_3) = 0.

{P}(A) ~=~ \genfrac{}{}{}{0}{1}{3} \cdot \genfrac{}{}{}{0}{23}{7} +\genfrac{}{}{}{0}{1}{3} \cdot \genfrac{}{}{}{0}{32}{7} +\genfrac{}{}{}{0}{1}{3} \cdot 0 ~\approx ~ 0{.}238