documentclass{report}
%usepackage{float}
usepackage{lipsum}
usepackage{graphicx}
begin{document}
lipsum[1-5]

begin{figure}[htb]
  centering
  includegraphics[width=0.8textwidth]{example-image-a}
end{figure}

begin{figure}[htb]
  centering
  includegraphics[width=0.8textwidth]{example-image-b}
end{figure}

begin{figure}[htb]
  centering
  includegraphics{example-image-c}
end{figure}
end{document}