44) 63n. 67n 62.60.ban

44) $$\frac{b^{3n} \cdot b^{7n}}{b^{2n} \cdot b^{0} \cdot b^{4n}} = \frac{b^{3n+7n}}{b^{2n+0+4n}} = \frac{b^{10n}}{b^{6n}} = b^{10n-6n} = b^{4n}$$

Ответ: $$b^{4n}$$