№ 1.
723 - (m + 238)= 345
m + 238 = 723 - 345
m + 238 = 378
m = 378 - 238
m = 140
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Проверка: 723 - (140 + 238) = 345
723 - 378 = 345
345 = 345
№ 2.
(х - 653) + 308 = 417
х - 653 = 417 - 308
х - 653 = 109
х = 109 + 653
х = 762
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Проверка: (762 - 653) + 308 = 417
109 + 308 = 417
417 = 417