Answer :
Given
Set A contains = 90 elements
Set B contains = 99 elements
A and B contains = 21 elements
Find
number of elements in Set S
Explanation
As we know
[tex]n(A\cup B)=n(A)+n(B)-n(A\cap B)[/tex]so,
[tex]n(A\cup B)=90+99-21=168[/tex]Total elements in S = elements in A or B + elements not in A or B
so,
[tex]168+24=192[/tex]Final Answer
Total elements in S = 192