640-40*(х+7)=160 и проверку

7х:640-40=1607х=600-1607х=440х=440:7х=63

640-40*(х+7)=160640-40x-280=160360-40x=160-40x=160-360-40x=-200x=-200/(-40)x=5Проверка640-40*(х+7)=160640-40*(5+7)=160640-200-280=160160=160