Решите уровнение : x+(x+10)-12+10=30
х + ( х + 10 ) - 12 + 10 = 30
2х + 10 - 12 + 10 = 30
2х + 8 = 30
2х = 30 - 8
2х = 22
х = 22 : 2
х = 11
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11 + ( 11 + 10 ) - 12 + 10 = 30
11 + 21 - 12 + 10 = 30
32 - 12 + 10 = 30
20 + 10 = 30
30 = 30