Age	S	B	A	Totals
Y	8	2	18	28
M	16	8	12	36
O	34	17	12	63
Totals	58	27	42	127

Using contingency table:
Find O' union (S union A)

In your post, the table is prepared very accurately - so accurately, 
that it is a pleasure to work with it and to help you.


        Now listen to me attentively.


They want you determine the number of elements in the set { O' union (S union A) }.


Here O' means the complement to the line O.  This complement is the union of lines Y and M.


So, to the lines Y and M, you should add the parts of columns S and A, that are outside lines Y and M.


Lines Y and M give you the totals 28 + 36 = 64.

To it, you should add the parts of columns S and A, that are outside the lines Y and M;
in other words, you should add (34+12) to 64.  It will give you the ANSWER  64 + (34+12) = 110.