% https://tex.stackexchange.com/q/224408/
\documentclass{article}
\usepackage{xsim}

\usepackage{needspace}

\DeclareExerciseProperty{hint}

% we’ll use a description list for the hints:
\newcommand\printhints{%
\begin{description}
\ForEachUsedExerciseByType{%
\def\ExerciseType{##1}%
\def\ExerciseID{##2}%
\GetExercisePropertyT{hint}
{%
\item[\XSIMmixedcase{\GetExerciseName}~##3]

       ####1%
    }%
}%

\end{description}
}

\newcommand\hint[1]{\SetExerciseProperty{hint}{#1}}

\begin{document}

\section{Problems}
% set hint through option:
\begin{exercise}[subtitle=Pythagoras,hint=This is a hint to the first problem.]
This is the first problem.
\end{exercise}
\begin{solution}
This is the solution to the first problem.
\end{solution}

\begin{exercise}[subtitle=Another Problem]
This is the second problem.
\end{exercise}
\begin{solution}
This is the solution to the second problem.
\end{solution}

% set hint with custom command:
\begin{exercise}[subtitle=Yet Another Problem]
This is the third problem.
\hint{This is a hint to the third problem.}
\end{exercise}
\begin{solution}
This is the solution to the third problem.
\end{solution}

\section{Hints}
\printhints

\section{Solutions}
\printsolutions[headings=false]

\end{document}