\[\boxed{\mathbf{3.}\mathbf{189}}\]
Пояснение.
Решение.
\[\textbf{а)}\ (25 + 12) \cdot 4 =\]
\[= 25 \cdot 4 + 12 \cdot 4 = 100 + 48 =\]
\[= 148\]
\[\textbf{б)}\ (100 + 30 + 2) \cdot 3 =\]
\[= 100 \cdot 3 + 30 \cdot 3 + 2 \cdot 3 =\]
\[= 300 + 90 + 6 = 396\]
\[\textbf{в)}\ (200 - 20) \cdot 5 =\]
\[= 200 \cdot 5 - 20 \cdot 5 =\]
\[= 1000 - 100 = 900\]
\[\textbf{г)}\ (300 - 10 - 1) \cdot 6 =\]
\[= 300 \cdot 6 - 10 \cdot 6 - 1 \cdot 6 =\]
\[= 1800 - 60 - 6 = 1734\]