How to solve this question

Question

Let A be a finite non-empty set with cardinality n. Let x and y be two of the elements of A. The number of subsets S $\subseteq$ A which include at least one of x or y is

Comments

it is just like, find the super keys where Relation have n attributes, and have a$_1$ and a$_2$ are candidate keys.

So, result is = $\color{red}{2^{n-1}}+\color{green}{2^{n-1}}-\color{brown}{2^{n-2}}$

red color part is for x (i.e., No.of super keys with a$_1$)

red color part is for y (i.e., No.of super keys with a$_2$)

brown color part is for intersection

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Thanks