9) ( A ∪ B)' = {10,11,12}
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Practice

1) Draw a Venn diagram for each of the following :
1) A'∩ B'.
2) A'.

2) Use Venn diagram : In a school, there are 20 teachers who teach Mathematics or English. Of these, 12 teach Mathematics and 4 teach both English and Mathematics. How many teach English only?

3) A and B are two sets. n(A) = 17,n(B) = 23 and n(A ∩ B). Find n(A ∪B). Set Theory