Step-by-step explanation:
[tex]a^{ \frac{4}{5} } . \sqrt{a {}^{21} } = a^{n} \\ {a}^{ \frac{4}{5} } . {a}^{ \frac{21}{2} } = {a}^{n} \\ {a}^{ \frac{113}{10} } = {a}^{n} \\ n \: = \frac{113}{10} [/tex]
