\subsection*{Combinatorics}
-\begin{itemize} \tightlist
- \item Arrangements \({n \choose k} = \frac{n!}{(n-k)}\)
- \item \colorbox{highlight}{Combinations} \({n \choose k} = \frac{n!}{k!(n-k)!}\)
- \item Note \({n \choose k} = {n \choose k-1}\)
-\end{itemize}
+\begin{align*}
+ \text{Arrangements} && {n \choose k} & = \frac{n!}{(n-k)} \\
+ \text{Combinations} && {n \choose k} & = \frac{n!}{k!(n-k)!}
+\end{align*}
+
+Note \({n \choose k} = {n \choose k-1}\)
+
+\begin{cas}
+ Keyboard \(\rightarrow\) Advance \(\rightarrow\) \keystroke{nCr}/\keystroke{nPr} \\
+ \-\hspace{1em} \texttt{nCr(n, r)} or \texttt{nPr(n, r)}
+\end{cas}
\subsection*{Distributions}