# [Tex/LaTex] Gather vs aligned – centered equation with one number

equations

What is the way to achieve something between gather and aligned?

\documentclass[12pt]{article}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage[utf8]{inputenc}

\begin{document}
\begin{gather}
3(a-x) = 3.5x + a - 1 \\
3a - 3x = 3.5x + a -1 \\
a = \frac{13}{4}x - \frac{1}{2}
\end{gather}

\begin{equation}
\begin{aligned}
3(a-x) = 3.5x + a - 1           \\
3a - 3x = 3.5x + a -1           \\
a = \frac{13}{4}x - \frac{1}{2}
\end{aligned}
\end{equation}
\end{document}


Result: But…
How to achieve something like this? I'd like to keep the centering. Is this possible somehow?

The gathered environment, used within math mode, is what you're looking for.

\documentclass[12pt]{article}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage[utf8]{inputenc}
\begin{document}
\begin{equation}
\begin{gathered}
3(a-x) = 3.5x + a - 1 \\
3a - 3x = 3.5x + a - 1 \\
a = \frac{13}{4}x - \frac{1}{2}
\end{gathered}
\end{equation}
\end{document} Wikibooks LaTeX has a fairly nice list of the different kinds of equation and align environments.