Ответ:

[tex](450 - x) + 180 = 580 \\ 630 - x = 580 \\ - x = 580 - 630 \\ - x = - 50 \\ x = 50[/tex]

(450 - х) + 180 = 580

(450 - х) = 580 - 180

450 - х = 400

х = 450 - 400

х = 50

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Проверка:

(450 - 50) + 180 = 580

400 + 180 = 580

580 = 580 - верно