5. An (BUC).

A = {1, 3, 4, 6, 8, 10}, B = {3, 7, 8, 10}, C = {4, 8, 11}

B∪C = {3, 7, 8, 10}∪{4, 8, 11} = {3, 4, 7, 8, 10, 11}

A∩(B∪C) = {1, 3, 4, 6, 8, 10}∩{3, 4, 7, 8, 10, 11} = {3, 4, 8, 10}

Ответ: {3, 4, 8, 10}