\[\boxed{\mathbf{10}\mathbf{.}}\]
\[\textbf{а)}\ 4 \cdot 2 + 15 = 8 + 15 = 23\]
\[2 \cdot 8 - 15 = 16 - 15 = 1\]
\[32 + 3 \cdot 4 = 32 + 12 = 44\]
\[50 - 2 \cdot 9 = 50 - 18 = 32\]
\[{б)\ 84 + 4 \cdot 4 = 84 + 16 = 100 }{100 - 4 \cdot 6 = 100 - 24 = 76}\]