7 7/30 - (5 11/30 - у) = 3 19/30
5 11/30 - у = 7 7/30 - 3 19/30 = 6 37/30 - 3 19/30 = 3 18/30
у = 5 11/30 - 3 18/30 = 4 41/30 - 3 18/30 = 1 23/30
у = 1 целая 23/30
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Проверка: 7 7/30 - (5 11/30 - 1 23/30) = 3 19/30
7 7/30 - (4 41/30 - 1 23/30) = 3 19/30
7 7/30 - 3 18/30 = 3 19/30
6 37/30 - 3 18/30 = 3 19/30
3 19/30 = 3 19/30