Homework template (latex)

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% LaTeX Example: Project Report
%
% Source: http://www.howtotex.com
%
% Feel free to distribute this example, but please keep the referral
% to howtotex.com
% Date: March 2011
%
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% How to use writeLaTeX:
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% You edit the source code here on the left, and the preview on the
% right shows you the result within a few seconds.
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% Bookmark this page and share the URL with your co-authors. They can
% edit at the same time!
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% You can upload figures, bibliographies, custom classes and
% styles using the files menu.
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% If you're new to LaTeX, the wikibook is a great place to start:
% http://en.wikibooks.org/wiki/LaTeX
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% Edit the title below to update the display in My Documents
%\title{Project Report}
%
%%% Preamble
\documentclass[paper=a4, fontsize=11pt]{scrartcl}
\usepackage[T1]{fontenc}
\usepackage{fourier}
\usepackage{setspace}

\usepackage[english]{babel}															% English language/hyphenation
\usepackage[protrusion=true,expansion=true]{microtype}	
\usepackage{amsmath,amsfonts,amsthm} % Math packages
\usepackage[pdftex]{graphicx}	
\usepackage{url}


%%% Custom sectioning
\usepackage{sectsty}
\allsectionsfont{\centering \normalfont\scshape}


%%% Custom headers/footers (fancyhdr package)
\usepackage{fancyhdr}
\pagestyle{fancyplain}
\fancyhead{}											% No page header
\fancyfoot[L]{}											% Empty
\fancyfoot[C]{}											% Empty
\fancyfoot[R]{\thepage}									% Pagenumbering
\renewcommand{\headrulewidth}{0pt}			% Remove header underlines
\renewcommand{\footrulewidth}{0pt}				% Remove footer underlines
\setlength{\headheight}{13.6pt}


%%% Equation and float numbering
\numberwithin{equation}{section}		% Equationnumbering: section.eq#
\numberwithin{figure}{section}			% Figurenumbering: section.fig#
\numberwithin{table}{section}				% Tablenumbering: section.tab#


%%% Maketitle metadata
\newcommand{\horrule}[1]{\rule{\linewidth}{#1}} 	% Horizontal rule

\title{
		%\vspace{-1in} 	
		\usefont{OT1}{bch}{b}{n}
		\normalfont \normalsize \textsc{University of Chinese Academy of Sciences, Math Department, Autumn 2017} \\
        %Grade (entered by Greg Lau): pts/40 pts} \\ [25pt]
		\horrule{0.5pt} \\[0.4cm]
		\huge Operating System Weekly Homework 03 \\
        %and 53;(Ch. 4)2,6,14,15 \\
		\horrule{2pt} \\[0.5cm]
}
\author{
		\normalfont 								\normalsize
        Xinze Li, Student ID 2015K8009906024\\[-3pt]		\normalsize
        %February 19, 2014
}
\date{}




%%% Begin document
\begin{document}
\maketitle
%\begin{section}

\section{Problem 1}
\subsection{description}


\subsection{solution}

\iffalse
\begin{equation}
\left\{
\begin{array}{l}
X\ 3\ 5\ 6\ 9\ (X\leq 3)\\
3\ X\ 5\ 6\ 9\ (3 < X\leq 5) \\
3\ 5\ X\ 6\ 9\ (5< X\leq 6)\\
3\ 5\ 6\ X\ 9\ (6<X\leq 9)\\
3\ 5\ 6\ 9\ X\ (9<X)
\end{array}
\right.
\end{equation}
\fi%use \iffalse to comment a section of codes

\begin{spacing}{1.8}
\begin{equation}
avg\_rsp\_time(X)\ =\ \left\{
\begin{array}{l}
X\ +\ 4.6\ (X\leq 3)\\
\dfrac{4X}{5}\ +\ 4.6\ (3 < X\leq 5) \\
\dfrac{3X}{5}\ +\ 4.6\ (5< X\leq 6)\\
\dfrac{2X}{5}\ +\ 4.6\ (6<X\leq 9)\\
\dfrac{X}{5}\ +\ 4.6\ (9<X)
\end{array}
\right.
\end{equation}
\end{spacing}

\section{Problem 2}
\subsection{description}


\subsection{solution}


\section{Problem 3}
\subsection{description}


\subsection{solution}

%%% End document
\end{document} 

Use pdflatex to edit it.