Ответ:
Пошаговое объяснение:
1)
21*(x-6) = 20(x+1) - 36(x+2)
21x - 126 = 20x + 20 - 36x - 72
21x - 126 = -16x - 52
21x + 16x = 126 - 52
37x = 74
x = 74 : 37
x = 2
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2)
18(x - 8) + 35(x + 5) = 8(7x + 1,5) + 10
18x - 144 + 35x + 175 = 56x + 12 + 10
53x + 31 = 56x + 22
56x - 53x = 31 - 22
3x = 9
x = 9 : 3
x = 3
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3)
9(2x + 5) - 16(5x + 7) = 42(x - 15) - 165
18x + 45 - 80x - 112 = 42x - 630 - 165
-62x - 67 = 42x - 795
42x + 62x = 795 - 67
104x = 728
x = 728 : 104
x = 7