$\left\{ \begin{gathered}
  x \hfill \\
  y \hfill \\ 
\end{gathered}  \right.\,\,\,\,\,\,\,\,\,\frac{y}{x} = \frac{1}{3} \to x = 3y$
$\begin{gathered}
  \left\{ \begin{gathered}
  x + 2 \hfill \\
  y - 2 \hfill \\ 
\end{gathered}  \right.\,\,\,\,\,\,\,\,\,\frac{{y - 2}}{{x + 2}} = \frac{1}{5} \to 5y - 10 = x + 2 \to 5y - x = 12 \hfill \\
 \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,2y = 12 \hfill \\
 \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,y = 6 \hfill \\ 
\end{gathered} $

پس تعداد غایب‌ها در انتهای کلاس y-2=4 نفر می‌باشد.