1) (у + 5/7) * 1/3 = 2 4/9
у + 5/7 = 2 4/9 : 1/3 = 22/9 * 3/1 = 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
7 7/21 * 1/3 = 2 4/9
154/21 * 1/3 = 2 4/9
154/63 = 2 28/63 = 2 4/9
2) (5/12 - х) : 1/2 = 2/9
5/12 - х = 2/9 * 1/2 = 1/9
х = 5/12 - 1/9 = 15/36 - 4/36 = 11/36
х = 11/36
Проверка: (5/12 - 11/36) : 1/2 = 2/9
4/36 : 1/2 = 4/36 * 2/1 = 8/36 = 2/9
3) (1 16/25 + х) * 4/5 = 4 2/25
1 16/25 + х = 4 2/25 : 4/5 = 102/25 * 5/4 = (51*1)/(5*2) = 51/10 = 5 1/10
х = 5 1/10 - 1 16/25 = 5 5/50 - 1 32/50 = 4 55/50 - 1 32/50 = 3 23/50
х = 3 целых 23/50
Проверка: (1 16/25 + 3 23/50) * 4/5 = 4 2/25
5 5/50 * 4/5 = 255/50 * 4/5 = (51*2)/(25*1) = 102/25 = 4 2/25