помогите с 4, 5, 6, 7 и 8, пожалуйста, очень необходимо

4) 21/53 = 220/(у+300)
21(у+300) = 53 220
у+300 = 11660 21
у = 555 5/21 - 300
у = 255 целых 5/21
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5) 29/30 = 78/(3у-2)
3у-2 = 30 78 29 = 2340 29 = 80 целых 20/29
у = (80 20/29 + 2)3 = 82 20/29 3 = 2398/29 1/3 = 2398/87 = 27 49/87
у = 27 целых 49/87
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6) 52/(4у+2) = 14/(3^3)
4у+2 = (52 27)14 = 1404/14 = 702/7 = 100 целых 2/7
у = (100 2/7 - 2)4 = 98 2/7 4 = 688/7 1/4 = 688/28 = 172/7 = 24 4/7
у = 24 целых 4/7
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7) 13/17 = (7+2у)/85
7+2у = (13 85)17 = 1105/17 = 65
у = (65 - 7)2 = 582
у = 29
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8) 55/90 = (6 - 5у)/18
6-5у = (55 18)90 = 990/90 = 11
у = (11 - 6)(-5) = -5/5
у = -1