--- a/day1/session4.tex	Wed Oct 28 14:44:47 2009 +0530
+++ b/day1/session4.tex	Wed Oct 28 15:17:40 2009 +0530
@@ -315,9 +315,15 @@
 \end{lstlisting}
 \end{frame}
 
+\subsection{Exercises}
 \begin{frame}[fragile]
-\frametitle{Exercises}
-
+\frametitle{Problem 1}
+\begin{align*}
+  x + y + 2z -w & = 3\\
+  2x + 5y - z - 9w & = -3\\
+  2x + y -z + 3w & = -11 \\
+  x - 3y + 2z + 7w & = -5\\
+\end{align*}
 \end{frame}
 
 \section{Summary}