How to use callouts behind the text With Latex like this?

Question

How to use callouts behind the text?

Answer 1

Adapting this MWE (adapted from this Simple speech bubbles, arrows or balloon like shapes in beamer) and using the math enviroment \ensuremath

\documentclass[12pt]{article}
\usepackage{amsmath,amssymb}
\usepackage{tikz}
\usetikzlibrary{calc,shapes.callouts}
\newcommand{\clouds}[2]{
        \tikz[remember picture,baseline]{\node[anchor=base,inner sep=0,outer sep=0]%
        (#1) {{\ensuremath{#1}}};\node[overlay,cloud callout,callout relative pointer={(-0.7cm,-0.2cm)},%
        aspect=2.5,draw=green] at ($(#1.south)+(4.2cm,1cm)$) {\ensuremath{#2}};}%
    }%

\begin{document}
\clouds{y'+xy=0}{\text{Being } \dfrac{y'}y=-x}
\end{document}

you can recreate your picture with the commands of LaTeX. To fixed the cloud you should to see the coordinates ($(#1.south)+(4.2cm,1cm)$) and callout relative pointer={(-0.7cm,-0.2cm)} for the correct positioning that it is depends from the type of equation or list of equations.