\documentclass[a4paper]{report}
\usepackage{polski}
\usepackage{tocloft}
\usepackage[utf8]{inputenc}

\newcommand{\listanswername}{Odpowiedzi do zadań}
\newlistof[chapter]{Answers}{ans}{\listanswername}

\newenvironment{Zadanie}[1]{%
  \refstepcounter{Answers}%
  \par\noindent\textbf{Zadanie \theAnswers. }\par
  \addcontentsline{ans}{Answers}{\protect\numberline{\theAnswers}#1}\par}

\begin{document}

\chapter{Zadanie b. proste}

\begin{Zadanie}{4}
Ile jest $2 \times 2$?
\end{Zadanie}

\begin{Zadanie}{zero}
Ile jest $2 - 2$?
\end{Zadanie}

\listofAnswers

\end{document}