\[\boxed{\mathbf{17.}}\]
\[Увеличить\ на\ 15:\]
\[25 + 15 = 40\]
\[35 + 15 = 50\]
\[45 + 15 = 60\]
\[50 + 15 = 65\]
\[60 + 15 = 75\]
\[70 + 15 = 85\]
\[80 + 15 = 95\]
\[Уменьшить\ на\ 15:\]
\[25 - 15 = 10\]
\[35 - 15 = 20\]
\[45 - 15 = 30\]
\[50 - 15 = 35\]
\[60 - 15 = 45\]
\[70 - 15 = 55\]
\[80 - 15 = 65\]