Step-by-step explanation:
We need to know
[tex]a^{-1} =\frac{1}{a}[/tex]
so
(a)
5^x = 125^(-1)
5^x = 5^(-3)
x = -3
(b)
3^(-3) * 10^(-3)
= (3*10)^(-3)
=1/27000
