[w*(5w^3)^-2]/(w^-4)
first rules to consider a^(-b)=1/a^b, (a^b)^c=a^(b*c), (a^b)*(a^c)=a^(b+c)
[w/(5w^3)^2]/(w^-4)
(w*w^4)/(25w^6)
w^5/(25w^6)
Then you have the quotient rule for powers (a^c)/(a^b)=a^(c-b)
1/(25w)
which we could state as:
(25w)^(-1) :P
