\[\boxed{\mathbf{16.}}\]
\[Увеличить\ на\ 100.\]
\[200 + 100 = 300\]
\[600 + 100 = 700\]
\[300 + 100 = 400\]
\[700 + 100 = 800\]
\[400 + 100 = 500\]
\[800 + 100 = 900\]
\[Уменьшить\ на\ 100.\]
\[200 - 100 = 100\]
\[600 - 100 = 500\]
\[300 - 100 = 200\]
\[700 - 100 = 600\]
\[400 - 100 = 300\]
\[800 - 100 = 700\]