\documentclass[12pt]{article}
\usepackage[margin=1in]{geometry}
\usepackage[all]{xy}
\usepackage{amsmath,amsthm,amssymb,color,latexsym}
\usepackage{geometry}
\geometry{letterpaper}
\usepackage{graphicx}
\newtheorem{problem}{Problem}
\newenvironment{solution}[1][\it{Solution}]{\textbf{#1. } }{$\square$}
\begin{document}
\noindent MAT 108 write here your section Spring 2018\hfill Problem Set \#\\
First name Last name. (MM/DD)
\hrulefill
\begin{problem}
Write here the text of the first homework problem.
\end{problem}
\begin{solution}
Write here the solution of the first homework problem.
\end{solution}
\begin{problem}
Write here the text of the second homework problem.
\end{problem}
\begin{solution}
Write here the solution of the second homework problem.
\end{solution}
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%%%%%Continue with this pattern if there are more%%%%%%%
%%%%%%%%%%%%%%%%%homework problems%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\end{document}
