fixed typo

inputs/lecture_12.tex

@@ -143,9 +143,8 @@ For the proof we need some prerequisites:
             a &: x \in A,\\
             b &: x \not\in A,\\
         \end{cases}
-        where $a \in \IF$ and $b \not\in \IF$
-        are chosen arbitrarily.
     \end{IEEEeqnarray*}
+    where $a \in \IF$ and $b \not\in \IF$ are chosen arbitrarily.
 \end{proof}
 
 \subsection{Linear Orders}