Question 88894
 1) x^-4 = 1/x^4 = (1/x^2)^2

2) (x^2y^6)^-3 = x^-6 y^-18 = 1/x^6 1/y^18 = (1/x^3)^2 (1/y^9)^2 = (1/x^3y^9)^2

3) x^4/x^6 = 1/x^2 = (1/x)^2

4) 12x^0x^2/4x^-6x^5 = 12x^2/4x^-1 = 3x^3