The code of the sketch, in LATEX language:

\documentclass{article}

\usepackage{tikz}

\begin{document}

  \begin{tikzpicture}

    \draw[fill] (0,0) circle [radius=0.025];
    \draw[fill] (3,0) circle [radius=0.025];
    \draw[fill] (6,0) circle [radius=0.025];

    \draw  (0,0) -- (6,0);
    
    \node [above] at (0,0) {x};
    \node [above] at (3,0) {y};
    \node [above] at (6,0) {z};

    \node (A) at (1.5,0) {$>$};
    \node [above] at (A) {f};

    \node (B) at (4.5,0) {$>$};
    \node [above] at (B) {g};
  
  \end{tikzpicture}

\end{document}