start by distributing the exponents outside the parenthesis. we would get:
(3^4)(m^-4)(n^8) / (2^3)(m^-6)(n^3)
first let's apply the exponents to the numbers (3 & 2) to get
81(m^-4)(n^8) / 8(m^-6)(n^3)
note that negative exponents are just flipped positive to the opposite side of the fraction. so (m^-4) in the numerator becomes (m^4) in the denominator. apply this and we get
81(m^6)(n^8) / 8(m^4)(n^3)
after we can simplify to reach
81(m^2)(n^5) / 8
