renamed problem

exam/packet.tex

@@ -141,7 +141,7 @@ Output:
 15 18
 \end{verbatim}
 \end{comment}
-% ========================= Problem 4 =========================
+% ========================= Problem 6 =========================
 \problem{Problem 6(.7): Six Seven}
 \textit{Difficulty: Easy}
 \begin{itemize}