Funes el memorioso

\documentclass[12pt]{article}
\usepackage[papersize={70mm, 35mm}, text={60mm, 25mm}]{geometry}
% For fancy fonts
\usepackage{fontspec}
\defaultfontfeatures{Scale=MatchLowercase, Mapping=tex-text}
\setmainfont[Ligatures={Common}, Numbers={OldStyle}]{Corbel}
\setsansfont[Scale=0.95]{Candara}
\setromanfont{Cambria}
\setmonofont{Monaco}

\usepackage{tikz}

\begin{document}
\pagestyle{empty}
\begin{figure}[h]
  \centering
  \begin{tikzpicture}
    [
      auto,
      line/.style ={draw, thick, -latex, shorten >=2pt},
      block/.style ={rectangle, text width=3em}
    ]
    
    \def\xdst{5cm}
    \def\ydst{-1.8cm}
    
    \node (X) at (0cm, 0cm) {$x$};
    \node (F) at (\xdst, 0cm) {$f(x)$};
    \node (B) at (\xdst, \ydst) {$b$};
    
    \path (X) edge [line, bend angle=10, bend left]
    node [above, midway] {easy} (F);
    \path (F) edge [line, bend angle=10, bend left, dashed, red]
    node [below, midway] {hard} (X);
    \path (X) edge [line, bend angle=15, bend right]
    node [midway, pos=.7,right, yshift=3mm] {easy} (B);
    \path (F) edge [line, dashed, red] node [right] {hard} (B);
  \end{tikzpicture}
\end{figure}
\end{document}