With some variations, to better see the effects.
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\documentclass[10pt,border=3mm,tikz]{standalone}\usetikzlibrary{matrix}\begin{document} \begin{tikzpicture}[ demo/.style={above,pos=.2,font={\tiny},red}, ] \matrix[ matrix of math nodes, inner sep=1pt, row sep=1em, column sep=2cm, ] (M) { ? & A & B & C \\ ? & E & F & G \\ } ; \draw[ ->] (M-1-2.east) -- node[above] {$ab$} (M-1-3.west); \draw[ ->] (M-1-3.east) -- node[demo] {$bc$}(M-1-4.west); \end{tikzpicture}\end{document}Kindly follow this checklist, before posting code snippets, to minimize our guessworking and reworking. Thank you.
