Tickbox quiz - Data Analysis

Hi Team,

In this question I understand Greg mentioned to choose table method and solve. But why cant we apply the formula, i.e. total=A+B-both where A = son in house B=daughter in house, basis the question.

100=80+40 -both which gives both as 20 and hence answer should be C, which is not the case. Correct answer is D.

I understodd the table method as explained by Greg, but just want to know that why do we not get the answer by applying the above formula?

Don’t forget the “none” as well in the formula.

A + B - Both + NEITHER = Total

Do we know what neither is here?