(х - 18) - 34 = 120
х - 18 = 120 + 34
х - 18 = 154
х = 154 + 18
х = 172
Проверка: (172 - 18) - 34 = 120
154 - 34 = 120
120 = 120
(х - 18) - 34 = 120
х - 18 = 120 + 34
х - 18 = 154
х = 154 + 18
х = 172
Проверка: (172 - 18) - 34 = 120
154 - 34 = 120
120 = 120