Ответ:\(315-(x+12)=140\)\(x+12=315-140=175\)\(x=175-12=163\).Проверка: \(315-(163+12)=140\).x = 163.\((y-420)+150=600\)\(y-420=600-150=450\)\(y=450+420=870\).Проверка: \((870-420)+150=600\).y = 870.