5) -14x⁷yz² ⋅ 1 2/7 x²y⁹z³;

$$-14x^7yz^2 \cdot 1\frac{2}{7}x^2y^9z^3 = -14x^7yz^2 \cdot \frac{9}{7}x^2y^9z^3 = (-14 \cdot \frac{9}{7}) \cdot (x^7 \cdot x^2) \cdot (y \cdot y^9) \cdot (z^2 \cdot z^3) = -2 \cdot 9 \cdot x^{7+2}y^{1+9}z^{2+3} = -18x^9y^{10}z^5$$

Ответ: -18x⁹y¹⁰z⁵