Answer:
512n^27·m^15
Explanation:
The rule of exponents applicable to this problem tells you ...
... (a^b·c^d)^e = a^(b·e)·c^(d·e)
That is, the exponent outside parentheses multiplies each of the exponents inside.
_____
(8n^9·m^5) = 8^3·n^(9·3)·m^(5·3)
... = 512·n^27·m^15