simplify expression (no negative exponents)
-2^-3(xy^3)^-2/x^-1y^-3
I got 1/-8x^2y^2
-2^-3(xy^3)^-2 = -1/(8x^2y^6)
x^-1y^-3 = 1/(xy^3)
now divide (multiply by the reciprocal) and you have
-1/(8x^2y^6) * xy^3 = -1/(xy^3)
or, you can just do it like this
-2^-3 (xy^3)^-2 (xy^3)
= 1/8 (xy^3)^-1
= -1/(8xy^3)