Simplify:

a. (5x^2)^3 x (x/4)^2 x (8/25x^5)
b. fifth root of a^3 x square root of a^5

a. Add the exponents of the various powers of x (x^6, x^2 and x^5), and take the product of the constant terms (125,1/16 and 8/25)for the constant coefficient

b. a^(3/5) * a^(5/2) = a^(3/5 + 5/2)
= a^(3.1)