1) 6 2/7 - 3 5/7 = 5 9/7 - 3 5/7 = 2 4/7
2) 4 1/6 * 2 4/7 = 25/6 * 18/7 = 75/7 = 10 5/7
3) 7 2/3 + 10 5/7 = 7 14/21 + 10 15/21 = 17 29/21 = 18 8/21
ответ: 18 8/21
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27% от 200 = 200 * 0,27 = 54
27% это 540 = 540 : 0,27 = 2000
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7 * ( x - 9) - (3x + 1 ) = 9
7x - 63 - 3x - 1 = 9
4x - 64 = 9
4x = 9 + 63
4x = 72
x = 72 : 4
x = 18