Let $X$ be a D17: Finite set such that
(i) | $E \subseteq X$ is a D78: Subset of $X$ |
Then
\begin{equation}
|E|
= |X| - |X \setminus E|
\end{equation}
(i) | $E \subseteq X$ is a D78: Subset of $X$ |
(i) | $E \subseteq X$ is a D78: Subset of $X$ |