5/12 - 7/9у = 10 5/12 - 3у
- 7/9у + 3у = 10 5/12 - 5/12
2 2/9у = 10
20/9у = 10
у = 10 : 20/9
у = 10 * 9/20
у = 9/2 = 4 целых 1/2 = 4,5
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Проверка: 5/12 - 7/9 * 9/2 = 10 5/12 - 3 * 9/2
5/12 - 7/2 = 10 5/12 - 27/2
5/12 - 42/12 = 125/12 - 162/12
- 37/12 = - 37/12