Question 294543
(5x^(-8))/(4^(-3)*z^2) does equal 320/(x^8 z^2)
Remember
5x^(-8)=1/5x^8
and 
4^(-3)=1/4^3
so you flip

5*4^3/x^8*z^2
5*64/x^8*z^2
320/(x^8 z^2)