А)3, 4/15+у=7, 11/15
у=7, 11/15-3, 4/15
у=4, 7/11
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3, 4/15+4, 7/15=7, 11/15
7, 11/15=7, 11/15
б)5, 4/13-х=4, 5/13
х=5, 4/13-4, 5/13
х=12/13
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5, 4/13-12/13=4, 5/13
4, 5/13=4, 5/13
х÷9=7, 4/9
х=7, 4/9*9
х=67
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67÷9=7, 4/9