Verified answer

(у + 5/7) · 1/3 = 2 4/9

(у + 5/7) · 1/3 = 22/9

у + 5/7 = 22/9 : 1/3

у + 5/7 = 22/9 · 3/1 = (22·1)/(3·1)

у + 5/7 = 22/3 = 7 1/3

у = 7 1/3 - 5/7 = 7 7/21 - 15/21 = 6 28/21 - 15/21 = 6 13/21

у = 6 целых 13/21

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Проверка: (6 13/21 + 5/7) · 1/3 = 2 4/9

                   (6 13/21 + 15/21) · 1/3 = 2 4/9

                   (6 28/21) · 1/3 = 2 4/9

                   154/21 · 1/3 = 2 4/9

                   154/63 = 22/9 = 2 4/9