(2 a^-4)(b^5)/(8 a^2)(b^-3)
2 (a^-4)(b^5)/(8 a^2)(b^-3)
Using positive exponent (b^-3) is move from the denominator to the numerator and become positive like wise (a^-4) is move from the numerator to the denominator
2(b^5)(b^3)/(8 a^2)( a^4) Multiply the coefficients. Then multiplying the variables by keeping the base and add the exponents.
Which results in getting
2(b^7)/8( a^6)
Simplifying we get (b^7)/4( a^6)