\[\boxed{\text{5.\ 57}}\]
\[\textbf{а)}\ 3 \cdot (x + y - z) =\]
\[= 3x + 3y - 3z\]
\[\textbf{б)}\ (m - n + z) \cdot 5 =\]
\[= 5m - 5n + 5z\]
\[\textbf{в)} - 3,8 \cdot (x - y - z) =\]
\[= - 3,8x + 3,8y + 3,8z\]
\[\textbf{г)}\ ( - x - y + z) \cdot ( - 4,5) =\]
\[= 4,5x + 4,5y - 4,5z\]
\[\textbf{д)}\ \frac{2}{3} \cdot ( - x + 2y - 3) =\]
\[= - \frac{2}{3}x + \frac{4}{3}y - 2\]
\[\textbf{е)} - \frac{3}{7} \cdot (2a - 5b + 4) =\]
\[= - \frac{6}{7}a + \frac{15}{7}b - \frac{12}{7}\]