Subplot does not give expected results

I used subplot code presented by overleaf and the only thing I change was adding my own figures. The result is totally wrong 🙂 I thought it may be the problem of the size but even by adjusting the at includegraphics was the same. Could you tell me what I am doing wrong ?

begin{figure}
     centering
     begin{subfigure}[b]{0.3textwidth}
         centering
         includegraphics[width=textwidth]{Figures_FCM/maturityf.eps}
         caption{$y=x$}
         label{fig:y equals x}
     end{subfigure}
     hfill
     begin{subfigure}[b]{0.3textwidth}
         centering
         includegraphics[width=textwidth]{Figures_FCM/colorf.eps}
         caption{$y=3sinx$}
         label{fig:three sin x}
     end{subfigure}
     hfill
     begin{subfigure}[b]{0.3textwidth}
         centering
         includegraphics[width=textwidth]{Figures_FCM/aggregate.eps}
         caption{$y=5/x$}
         label{fig:five over x}
     end{subfigure}
        caption{Three simple graphs}
        label{fig:three graphs}
end{figure}

The result takes the whole page and the 3rd image goes beyond the page…