\documentclass{article}
\usepackage[margin=1in]{geometry}
\title{My document}
\author{David and Collaborators}
\begin{document}
\maketitle
\section{Problem 1}
\section*{Solution}
This is problem 2 from the textbook. The solution is ... 
\[ 
\int_0^\infty \frac{\partial f}{\partial x} \, dx = g 
\]

\[ \left[ \begin{array}{ccc}
1 & 0 & 1 \\
0 & 1 & \int_0^y f(x) \, dx \\
1 & 0 & x \end{array}\right] 
\]
\section{Problem 1}
\section*{Solution}
\end{document}
