\[\boxed{\mathbf{7}\mathbf{.}}\]
\[\textbf{б)}\ 40\ :5 + 55 = 8 + 55 = 63\]
\[40 - 35\ :5 = 40 - 7 = 33\]
\[4 \cdot 8 - 16 = 32 - 16 = 16\]
\[90 - 3 \cdot 8 = 90 - 24 = 66\]
\[61 + 27\ :3 = 61 + 9 = 70\]
\[50\ :5 + 0 = 10 + 0 = 10\]
\[4 \cdot 7 + 72 = 28 + 72 = 100\]
\[100 - 36\ :4 = 100 - 9 = 91\]
\[35 - 5 \cdot 7 = 35 - 35 = 0\]