111-3(x-3(x-3(x-3)))=3

111-3(х-3(х-3(х-3)))=3, 111-3(х+6х-27)=3, 111-3(7х-27)=3, 111-21х+81=3, 192-21х=3, -21х=3-192, -21х=-189, х=9. Ответ: 9.