We have the next information:
S = 105 elements
A and B are subsets of S.
A = 19 elements
B = 48 elements
Set A and B have 4 elements in common.
Now, we need to find :
Total elements in ( A or B) = elements in A + elements in B - elements in common.
Replacing:
Total elements in ( A or B) = 19 + 48 - 4
Total elements in ( A or B) = 63