Please consider posting complete examples such that others do not have to reverse engineer commands like \redtt
. As for your question, you can use aligned
or an array
.
\documentclass{article}
\usepackage{amsmath}
\usepackage{array}
\usepackage{xcolor}
\newcommand{\redtt}[1]{\textcolor{red}{\mathtt{#1}}}
\begin{document}
\begin{align*}
\left[\begin{array}{ccc|c}
1 & 0 & 0 & \redtt{b1} \\
0 & 1 & 1 & \redtt{b2} \\
0 & 0 & 1 & \redtt{b3}
\end{array}\right]\quad \longrightarrow\quad \begin{aligned}
x &= \redtt{b1} \\
y + z &= \redtt{b2} \\
z &= \redtt{b3}\\
\end{aligned} \\
\end{align*}
\begin{align*}
\left[\begin{array}{ccc|c}
1 & 0 & 0 & \redtt{b1} \\
0 & 1 & 1 & \redtt{b2} \\
0 & 0 & 1 & \redtt{b3}
\end{array}\right]\quad \longrightarrow\quad \begin{array}{@{}r<{{}}@{}>{{}}l@{}}
x &= \redtt{b1} \\
y + z &= \redtt{b2} \\
z &= \redtt{b3}
\end{array} \\
\end{align*}
\end{document}

IMHO aligned
looks better but in the array you maintain the same spacing between the rows as in the matrix. (Of course one can adjust aligned
to give the same spacing, and so on.)
ADDENDUM: As barbara beeton points out, if you only have a one-line equation it is more appropriate to use \[...\]
.
\documentclass{article}
\usepackage{amsmath}
\usepackage{array}
\usepackage{xcolor}
\newcommand{\redtt}[1]{\textcolor{red}{\mathtt{#1}}}
\begin{document}
\[
\left[\begin{array}{ccc|c}
1 & 0 & 0 & \redtt{b1} \\
0 & 1 & 1 & \redtt{b2} \\
0 & 0 & 1 & \redtt{b3}
\end{array}\right]\quad \longrightarrow\quad \begin{aligned}
x &= \redtt{b1} \\
y + z &= \redtt{b2} \\
z &= \redtt{b3}\\
\end{aligned}
\]
or
\[
\left[\begin{array}{ccc|c}
1 & 0 & 0 & \redtt{b1} \\
0 & 1 & 1 & \redtt{b2} \\
0 & 0 & 1 & \redtt{b3}
\end{array}\right]\quad \longrightarrow\quad \begin{array}{@{}r<{{}}@{}>{{}}l@{}}
x &= \redtt{b1} \\
y + z &= \redtt{b2} \\
z &= \redtt{b3}
\end{array} \]
\end{document}
\[...\]
orequation*
(or forget the*
if you would like this numbered.