\[\boxed{\mathbf{91}.}\]
\[x = 100 - 9y\]
\[1)\ y = 8:\]
\[x = 100 - 9 \cdot 8 = 100 - 72 =\]
\[= 28.\]
\[2)\ y = 0:\]
\[x = 100 - 9 \cdot 0 = 100 - 0 =\]
\[= 100.\]