'Inverse' questions like this are very tricky :) It could have been produced using any number of documentclass However, if I had to bet, my money would go on the exam documentclass which provides many useful features for typesetting exams- the only one I have used in the MWE is the questions environment, but there is a lot more you can do with it (see the documentation for details).

I've used the mdframed package for the framing, but it might have been done using an \fbox
\documentclass[11pt]{exam}
\usepackage{mdframed}
\setlength{\parindent}{0mm}
\begin{document}
\begin{mdframed}
{\bfseries Math 114E}
{\itshape Practice Midterm 2 Solutions \hfill March 18, 2012}
\end{mdframed}
\begin{questions}
\question The equation of the sphere is $(x-3)^2+y^2+(z+4)^2=25$. To
find a place, we need a normal vector and a point on the plane. To find the
normal, we take the gradient of our surface to get
\[
\vec{u}=(2(x-3),2y,2(z+4))=(8,6,0)
\]
So (dividing by $2$) our normal vector is $\vec{u}=(4,3,0)$, and our point
is $(7,3,-4)$, so we are all set.
\end{questions}
\end{document}
The same effect could easily have been created using the article documentclass as well. This does not have a question environment built-in though, so I created one based on the enumerate environment, using the enumitem to do the heavy lifting for me.

\documentclass[11pt]{article}
\usepackage{mdframed}
\usepackage{enumitem}
\newlist{questions}{enumerate}{5}
\setlist[questions]{label*=\arabic*.}
\setlength{\parindent}{0mm}
\begin{document}
\begin{mdframed}
{\bfseries Math 114E}
{\itshape Practice Midterm 2 Solutions \hfill March 18, 2012}
\end{mdframed}
\begin{questions}
\item The equation of the sphere is $(x-3)^2+y^2+(z+4)^2=25$. To
find a place, we need a normal vector and a point on the plane. To find the
normal, we take the gradient of our surface to get
\[
\vec{u}=(2(x-3),2y,2(z+4))=(8,6,0)
\]
So (dividing by $2$) our normal vector is $\vec{u}=(4,3,0)$, and our point
is $(7,3,-4)$, so we are all set.
\end{questions}
\end{document}
In both cases, tweaks to the page geometry could be achieved using the geometry package.
cvmodern. – doncherry Mar 19 '12 at 09:42