%% 
%%  Ein Beispiel der DANTE-Edition
%%  Mathematiksatz mit LaTeX
%%  3. Auflage
%%  Beispiel 09-26-3 auf Seite 207.
%%  Copyright (C) 2018 Herbert Voss
%% 
%%  It may be distributed and/or modified under the conditions
%%  of the LaTeX Project Public License, either version 1.3
%%  of this license or (at your option) any later version.
%%  See http://www.latex-project.org/lppl.txt for details.
%% 
%% ==== 
% Show page(s) 1
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\documentclass[10pt]{exaartplain}
\pagestyle{empty}
\setlength\textwidth{170.40707pt}
\AtBeginDocument{\setlength\parindent{0pt}}
%StartShownPreambleCommands
\usepackage{witharrows}% lädt automatisch tikz
\usetikzlibrary{calc}
%StopShownPreambleCommands
\begin{document}
$\begin{WithArrows}[ll,interline=5mm,xoffset=5mm,
  TikzCode={\draw[rounded corners,
  every node/.style = {circle, draw, auto = false,
  inner sep = 1pt, fill = gray!50, font = \tiny }]
    let \p1 = (#1), \p2 = (#2) in
    \ifdim \x1 > \x2 (\p1) --
    node {#3} (\x1,\y2) -- (\p2)
    \else (\p1) -- (\x2,\y1) -- node {#3} (\p2)
    \fi ;} ]
E & \Longleftrightarrow \frac{(x+4)}3 +
    \frac{5x+3}5 = 7 \Arrow{$\times 15$}\\
& \Longleftrightarrow 5(x+4) + 3(5x+3) = 105 \\
& \Longleftrightarrow 5x+20 + 15x+9 = 105 \\
& \Longleftrightarrow 20x+29 = 105 \Arrow{$-29$}\\
& \Longleftrightarrow 20x = 76 \Arrow{$\div 20$}\\
& \Longleftrightarrow x = \frac{38}{10}
\end{WithArrows}$
\end{document}