\[\boxed{\mathbf{3.}\mathbf{246}}\]
Пояснение.
Решение.
\[\textbf{а)}\ 12 \cdot (70 + b) =\]
\[= 12 \cdot 70 + 12 \cdot b = 840 + 12b\]
\[\textbf{б)}\ 38 \cdot (21 - b) =\]
\[= 38 \cdot 21 - 38 \cdot b = 798 - 38b\]
\[\textbf{в)}\ (x - 14) \cdot 19 =\]
\[= x \cdot 19 - 14 \cdot 19 = 19x - 266\]
\[\textbf{г)}\ (16 + z) \cdot 13 =\]
\[= 16 \cdot 13 + z \cdot 13 = 208 + 13z\]