1) - 7 * ( 2 - 3х) = 56
- 14 + 21х = 56
21х = 56 + 14
21х = 70
х = 70 : 21
х = 3 ц 1/3
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2) (5+ 7а) * 15 = - 30
75 + 105а = - 30
105а = - 30 - 75
105а = - 105
а = - 105 : 105
а = -1
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