How to make a system of equations with a number after every line and a tall curly brace on the left

Question

So, i have this code:

\begin{align}
S(t+\Delta) &= S(t)-\beta S(t)I(t)\Delta + \phi R(t) \Delta \label{S}\\
I(t+\Delta) &= I(t) + \beta S(t)I(t) \Delta - \gamma I(t) \Delta \label{I}\\
R(t+\Delta) &= R(t) + \gamma I(t)\Delta - \phi R(t)\Delta \label{R} \end{align}

I want this with the numbering after every line (i already have that); but i want an '{' in front of the three lines. Is that possible?

Answer 1

From this answer:

\documentclass{article}
\usepackage[overload]{empheq} % (already load amsmath)
\begin{document}
ABC
\begin{align}[left=\empheqlbrace]
S(t+\Delta) &= S(t)-\beta S(t)I(t)\Delta + \phi R(t) \Delta \label{S}\\
I(t+\Delta) &= I(t) + \beta S(t)I(t) \Delta - \gamma I(t) \Delta \label{I}\\
R(t+\Delta) &= R(t) + \gamma I(t)\Delta - \phi R(t)\Delta \label{R}
\end{align}
From equation \eqref{S}, \eqref{I} and \eqref{R}, we have blah blah blah
\end{document}