Chapter 2 - Set Theory - 2.3 Venn Diagrams and Set Operations - Exercise Set 2.3 - Page 81: 10

B' = {1,2,3,4,5,10,11, ... 20}

U = {1,2,3,4...20} B = {6,7,8,9} The set B' contains the elements that are not present in the set B. The elements of set B i.e. 6,7,8,9 must not be present in set B. The elements of B' are 1,2,3,4,5,10,11, ... 20. Therefore B' = {1,2,3,4,5,10,11, ... 20}