(2/4)*(1/3)=2/12=1/6 - 2 рыбы
(2/4)*(1/3)=2/12=1/6 - 2 птицы
(2/4)*(2/3)+(2/4)*(2/3)=4/12+4/12=8/12=2/3 - птица и рыба
(2/4)*(1/3)=2/12=1/6 - 2 рыбы
(2/4)*(1/3)=2/12=1/6 - 2 птицы
(2/4)*(2/3)+(2/4)*(2/3)=4/12+4/12=8/12=2/3 - птица и рыба