\documentclass[11pt]{article}

\usepackage{fancyhdr}
\usepackage[margin=1in,head=.1in,includehead]{geometry}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsthm}

\usepackage{enumitem}

\usepackage[bookmarksnumbered]{hyperref}

\DeclareSymbolFont{AMSb}{U}{msb}{m}{n}

\DeclareMathSymbol{\N}{\mathbin}{AMSb}{"4E}
\DeclareMathSymbol{\Z}{\mathbin}{AMSb}{"5A}
\DeclareMathSymbol{\R}{\mathbin}{AMSb}{"52}
\DeclareMathSymbol{\Q}{\mathbin}{AMSb}{"51}
\DeclareMathSymbol{\C}{\mathbin}{AMSb}{"43}
\DeclareMathSymbol{\F}{\mathbin}{AMSb}{"46}
\DeclareMathSymbol{\T}{\mathbin}{AMSb}{"54}

\newcommand{\im}{\operatorname{Im}}
\newcommand{\re}{\operatorname{Re}}

\newcommand{\set}[1]{\left\{#1\right\}}

\newtheorem*{claim}{Claim}
\newtheorem*{theorem}{Theorem}
\newtheorem*{lemma}{Lemma}
\newtheorem*{corollary}{Corollary}
\newtheorem*{prop}{Proposition}

\def\thesection{Question \arabic{section}}
\def\thesubsection{Part \Alph{subsection}}
\def\thesubsubsection{\roman{subsubsection}.}

\pagestyle{fancy}
\chead{Math 123A, Assignment \#1}
\lhead{Octember $1^{\text{st}}$, 2101}

\rhead{Your Name}
\rfoot{\thepage}
\cfoot{}
\lfoot{}

\begin{document}
% This is a comment and won't appear in the document.
\section{}
This is the first question.

\section{}
This is the second question. It has some parts.

\subsection{}
This is the first part, where we compute a solution to $x^2 - 4x + 3 = 0$ using the quadratic formula and a long computation.
\begin{align*}
	x &= \frac{4 \pm \sqrt{(-4)^2 - 4\cdot1\cdot3}}{2\cdot1} \\
	&= \frac{4 \pm \sqrt{16 - 12}}{2} \\
	&= 2 \pm 1.
\end{align*}
We conclude that the solutions are $x \in \left\{ 1, 3 \right\}$.
Note that all solutions are elements of $\R$, that is, the real numbers: $\im(x) = 0$.

\subsection{}
Here is another subsection where we don't do anything fancy.
You can find more information than you ever wanted about how to use \LaTeX{} at \url{https://tobi.oetiker.ch/lshort/lshort.pdf}.

\section{}
\begin{claim}
	There are infinitely many prime numbers.
\end{claim}

\begin{proof}
	Left as an exercise to the reader.
\end{proof}
\end{document}
