This situation is exactly what the `cases`

environment from the `amsmath`

package was designed for. If you put

```
\usepackage{amsmath}
```

in your preamble then you can wite

```
\[ \begin{cases}
0 & x\leq 0 \\
\frac{100-x}{100} & 0\leq x\leq 100 \\
0 & 100\leq x
\end{cases}
\]
```

to adapt your example with the correct size bracket.

As for not being able to use TeX-like syntax to write equations on this site: this is a deliberate choice. Most of the time we actually want to talk about the TeX source here rather than the equations (or whatever) it produces; and there are times when it could be actively confusing to have a TeX-like process to produce images that isn't actually TeX (in its full, Turing-complete, confusing glory...)

(See the discussion on meta for more on this, if you're interested.)

One possibility: I used `\DeclarePairedDelimiterX`

from the `mathtools`

package to define a `\MeijerM`

command with three arguments which is responsible to typeset the delimited matrix; then I defined `\MeijerG`

having eight arguments (the first one is optional and will be passed as the optional argument to `\MeijerM`

); using the `\WithSuffix`

command from the `suffix`

package to provide the starred version `\MeijerG*`

:

```
\documentclass[11pt]{article}
\usepackage{suffix}
\usepackage{mathtools}
\DeclarePairedDelimiterX\MeijerM[3]{\lparen}{\rparen}%
{\begin{smallmatrix}#1 \\ #2\end{smallmatrix}\delimsize\vert\,#3}
\newcommand\MeijerG[8][]{%
G^{\,#2,#3}_{#4,#5}\MeijerM[#1]{#6}{#7}{#8}}
\WithSuffix\newcommand\MeijerG*[7]{%
G^{\,#1,#2}_{#3,#4}\MeijerM*{#5}{#6}{#7}}
\begin{document}
\[
\MeijerG*{m}{n}{p}{q}{a_1, \dots, a_p}{b_1, \dots, b_q}{z}\quad
\MeijerG[\big]{m}{n}{p}{q}{a_1, \dots, a_p}{b_1, \dots, b_q}{z}\quad
\MeijerG[\Bigg]{m}{n}{p}{q}{a_1, \dots, a_p}{b_1, \dots, b_q}{z}
\]
\end{document}
```

The size of delimiters in the second and third examples is obviously wrong, but I just included them to test the functionality of the defined commands. Also, I used simple sub/superscripts to typeset the first four arguments, but of course you can use one of your proposed variants instead.

## Best Answer

LaTeX is very flexible. Although it is not WYSIWYG you can write it in a very logical way. So if you want to have to have f(x) precede your cases, just write it that way. Here with the example of the linked question.