Question

If n(A)=20, n(B)=18 and n(A union B)=5, calculate n(A-B)
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Answer 1

The union os two sets includes all the values which lie in either of the sets. And so, it can never be less than the elements in any of the sets.

I've manipulated the given information accordinly.

$\sf {n(A) = 20} }$

$\sf {n(B) = 18} }$

$\sf {n(A \cap B) = 5}$

$\sf {n(A - B) = n(A) - n(A \cap B) }$

=> n(A - B) = 20 - 5

=> n(A - B) = 15

Answer 2

Answer:

sets and relations

applied maths

33 15 13 is the ans