sh]{babel}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}

\usepackage{amssymb}
\usepackage{amsthm}

\newcounter{dummy} \numberwithin{dummy}{section}

\newtheorem{thm}[dummy]{Theorem}
\newtheorem{lem}[dummy]{Lemma}

% También podría poner ordinales.

\usepackage{lmodern}
\usepackage{graphicx}
\usepackage{amsmath} 
\usepackage{hyperref}
\usepackage{bookmark}

\begin{document}

\chapter{Introduction}

%TODO no sé si es subsection
\section{Basics}

\begin{lem}
\label{fundamental}
    Water is wet.
\end{lem}

\begin{proof}
   It's obvious.
\end{proof}

\begin{thm}
    Snow will be wet when it melts.
\end{thm}
\begin{proof}

We'll use Lemma \ref{fundamental}.

    Snow is frozen water$\underset{\text{Lemma\ \ref{fundamental}}}{\Rightarrow}$ it will be wet when it melts.
\end{proof}

\end{document}

(Off-topic: but please don't load the same package multiple times)



Q:

Modifying existing Shopify theme vs Building from scratch

I'm starting a new project where I'll be creating a Shopify Store for a clothing company, and I'm curious as to which of these 'paths' makes more sense, as far as cost and time are concerned.
My primary goal is getting the store up and running as quickly as possible. That being said, I'm wondering what the pros and cons of modifying a theme vs creating a brand new, custom one are.
My Concerns:
If I purchase the existing theme that most closely matches my clients needs, how likely is it that I'll spend more time modifying it than if I'd just created one from scratch?
My instinct would be to purchase a theme, modify, gut & replace the HTML/CSS/Javascript that isn't relevant to my project, while keeping the cart system and other e-commerce related features intact. I'll be hiring other coders to assist in areas where I have less experience (liquid templating, dealing with AJAX/Javascript). 
Would it make more sense to create all the HTML/CSS assets myself, and hire a coder who specializes in creating Shopify themes to help with the rest?
For instance: I could start with this very sparse Shopi