Question

If n(a)=7,n(b)=5,n(a-b)=3then n(a union b) =

Answer 1

HEY !!!!

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n(A)=n(A-B) + n(A intersection B)

n(A intersection B)= n(A)-n(A - B)

=7-3=4

n(A union B) = n(A) + n(B)-n(A intersection B)

=7+5-3

=9

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Thanks !!!