Several lines of formulas to the left of one curly brace pointing to equation number
Looks like you have an extra line break \\
to the right of your label. If you delete it, the output should look fine.
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align}
\left.
\begin{array}{ll}
a = b + c \\
& \dots \\
a = b + c \\
& \dots \\
a = b + c
\end{array}
\right\} \label{formulas}
\end{align}
\end{document}
I would use rcases
from the mathtools
package for this- it loads and extends the amsmath
package.
Code
% arara: pdflatex
\documentclass{article}
\usepackage{mathtools}
\begin{document}
\begin{equation}
\begin{rcases}
a = b + c \\
& \dots \\
a = b + c \\
& \dots \\
a = b + c
\end{rcases}
\label{formulas}
\end{equation}
\end{document}