a) $$ \frac{x^{n+m}}{a^{n+1}a^6} = \frac{x^{n+m}}{a^{n+1+6}} = \frac{x^{n+m}}{a^{n+7}} $$
Ответ: $$\frac{x^{n+m}}{a^{n+7}}$$