\documentclass[12pt]{amsart}

\usepackage{verbatim}
\usepackage{fullpage}

\input{isomath}
\input{mathenv}

\renewcommand{\theequation}{\arabic{problem}.\arabic{equation}}
\renewcommand{\labelenumi}{(\alph{enumi})}
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\begin{document}
\title{Assignment 1 $\cdot$ MAT 999 $\cdot$ Fall 1798}
\author{C. F. Gauss}
\date{\today}
\maketitle

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\begin{problem*}[1]
What is 101+2?

\begin{answer}
103.
\end{answer}
\end{problem*}

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\begin{problem*}[2]
What is 107+2?

\begin{answer}
109.
\end{answer}
\end{problem*}

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\begin{problem*}[3]
Prove that there are infinitely many primes of the form $p$, $p+2$.

\begin{proof}
Well, this problem sounded easy but I haven't proved it yet \ldots
\end{proof}
\end{problem*}

\end{document}