\[\boxed{\mathbf{3.}\mathbf{56}}\]
Пояснение.
Решение.
\[\textbf{а)}\ 75 \cdot 6 =\]
\[= 75 + 75 + 75 + 75 + 75 + 75\]
\[\textbf{б)}\ k \cdot 7 =\]
\[= k + k + k + k + k + k + k\]
\[\textbf{в)}\ (a + b) \cdot 3 =\]
\[= (a + b) + (a + b) + (a + b)\]