\[\boxed{\mathbf{38.}}\]
\[\textbf{а)}\ 4 \cdot 6 - 6 = 24 - 6 = 18\]
\[50 - 6 \cdot 3 = 50 - 18 = 32\]
\[40 - 16\ :4 = 40 - 4 = 36\]
\[50 - 5 \cdot 3 = 50 - 15 = 35\]
\[30\ :5 - 6 = 6 - 6 = 0\]
\[19 + 36\ :6 = 19 + 6 = 25\]
\[\textbf{б)}\ 28 + 9 \cdot 8 = 28 + 72 = 100\]
\[63\ :7 + 69 = 9 + 69 = 78\]
\[56 - 8 \cdot 7 = 56 - 56 = 0\]