\[Страница\ 16.\]
\[\boxed{\mathbf{38.}}\]
\[99,\ 97,\ 91,\ 79,\ 77,\ 71,\ 19,\ 17,\ 11.\]
\[1)\ В\ порядке\ возрастания:\]
\[11,\ 17,\ 19,\ 71,\ 77,\ 79,\ 91,\ 97,\ 99.\]
\[2)\ 99 - 79 = 20\]
\[99 - 19 = 80\]
\[79 - 19 = 60\]
\[3)\ 11 + 19 = 30\]
\[71 + 17 = 88\]
\[79 + 11 = 90\]
\[\boxed{\mathbf{39.}}\]