\documentclass[12pt]{article}
\textwidth=6.75in
\textheight=9.25in
\topmargin=-.75in
\oddsidemargin=-10pt
\evensidemargin=-.5in
\parskip=10pt  
\parindent=10pt %% <----------

\usepackage{amssymb,latexsym}

% We add packages so that we can get extra symbols for example:
%\Box, which will be used below

% The % sign is used to write comments

\begin{document} 
%need to start the document.  no text that is above this will appear

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%To write text just go ahead and write:



% To write math, enclose the expression with either $ symbols or $$ symbols:

\noindent{\bf Theorem.}
Let $f(x)$ %one dollar sign means in-line math
 be a function and let
$$
g(x) = ??? .
$$
%two dollar signs means displayed math

\vskip 20pt %vertical skip of 20 points

\noindent % at the top of the document by the %% <---------- you can set the amount of indent
{\it Proof.} Write your proof here. 




\hfill $\Box$ %this denotes the end of your proof.

\vskip 20pt % vertical skip of 20 points
Start your paper like this:

\begin{center}
{\bf \uppercase{Title of your thesis}}
\vskip 5pt
{\it Your Name}
\end{center}

Next, write an abstract, which is a very brief summary of the problem and your results:

\vskip 20pt
\centerline{\bf Abstract}

\noindent
Abstract here.

\vskip 20pt

Your thesis will consist of sections, with the first one being an introduction.

\section{Introduction}

Other sections could be Algorithm or Main Result or Preliminaries.

\vskip 20pt

For help with symbols, go to {\tt http://detexify.kirelabs.org/classify.html}
\end{document}