$\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.