Today, I wanted to write a system of linear equations in a triangular form using \(\LaTeX\). As you may know, \(\LaTeX\) and especially the `amsmath`

package offers many ways to align equations. I wanted to achieve something like

I tried several ways including the `align`

or `equation`

(with `split`

) environment. But for some reason, all of them messed up.

Finally, I found the `alignat`

environment, also from the `amsmath`

package, which did what I wanted. This environment lets you explicitly set the spacing between the equations. The MWE looks like

```
\documentclass{scrartcl}
\usepackage{amsmath}
\begin{document}
\begin{alignat*}{2}% Use alignat when you wish to have individual equation numbering
&l_{00} y_{0} && = b_{0} \\
&l_{10} y_{0} + l_{11} y_{1} && = b_{1} \\
&l_{20} y_{0} + l_{21} y_{1} + l_{22} y_{2} && = b_{2}
\end{alignat*}
\end{document}
```

As the official documentation (p. 7) explains, the mandatory argument is the number of “equation columns” which can be calculated as the maximum number of `&`

in a row + 1 divided by 2^{1}.