\[\boxed{\mathbf{3.}\mathbf{247}}\]
Пояснение.
Решение.
\[\textbf{а)}\ (25 + 250) \cdot 4 =\]
\[= 25 \cdot 4 + 250 \cdot 4 =\]
\[= 100 + 1000 = 1100\]
\[\textbf{б)}\ 6 \cdot (13 + 150) =\]
\[= 6 \cdot 13 + 6 \cdot 150 = 78 + 900 =\]
\[= 978\]
\[\textbf{в)}\ 8 \cdot 29 + 8 \cdot 21 =\]
\[= 8 \cdot (29 + 21) = 8 \cdot 50 = 400\]
\[\textbf{г)}\ 63 \cdot 237 + 63 \cdot 763 =\]
\[= 63 \cdot (237 + 763) = 63 \cdot 1000 =\]
\[= 63\ 000\ \]