Let us first determine the row/column totals of the given table, which is the sum of all counts in the row/column: \(\begin{array}{c|c} \text{ Yonger } & \text{ Middle} & \text{ Older } & \text{ Row } & \text{ total} \\ \hline Yes& 78 &49& 21& 78+49+21=148 \\ \hline No &4 &21& 46 & 4+21+46=71 \\ \hline \text{ Column total }& 78+4=82& 49+21=70 &21+46=67& 148+71=219 \end{array}\)

We the note that the table contains 219 students in total (which is given in the bottom right corner of the above table), while 21 of the 219 students are older and Facebook users (which is given in the row ”Yes” and in the column *Older” of the above table).

\(\frac{21}{219}=\frac{7}{73} \sim 0.09589=9.589\%\)

Thus 9.589% of the students who responded were older Facebook users.