%%% Preamble starts here.
\documentclass{math215}

% Include any special packages you might use.  Uncomment the
% following to use Times as the default font insteand of
% TeX's default font of Computer Modern.
\usepackage{times,txfonts}

% The following commands set up the material that appears
% in the header.
\doclabel{Math 215: Homework 1a}
\docauthor{Your name here.}
\docdate{January 25, 2013}

% I've provided a file (math215extras.tex) with some commonly used extra 
% commands. If you've downloaded it, you can include it in your document
% by uncommenting the line below.  Feel free to make changes to that file.
\input{math215extras.tex}

%%%% Main document starts here.

\begin{document}

\begin{proposition}{1.7} If $m$ is an integer, then $0+m=m$
and $1\cdot m=m$.
\end{proposition} 
\begin{pf}
Your proof goes here.
\end{pf}

\begin{proposition}{1.8} If $m$ is an integer, then $(-m)+m=0$.
\end{proposition}
\begin{pf}
Your proof goes here.
\end{pf}

\begin{proposition}{1.11(iii)} Let $m$, $n$ and $p$ be integers.
	Then $m+(n+p)=(p+m)+n$.
\end{proposition}
\begin{pf}
Your proof goes here.
\end{pf}

\end{document}