Simplify Each expression. State the answer using positive exponents. I don't understand how to simplify :/

1.       (5²)(5^-4)/5³            2.       (2mn³)^-3

 

 

 

 

3.       (5m⁴n⁰)(m^1/4n^-3/2)             4          (8x^1/5/64x^3/4)^2/3