x^2*x^8+x^13/x^3
=x^(2+8)+x^(13-3)
=x^10+x^10
=2x^10
a^19/a^12/a^3
=a^(19-12-3)
=a^4
(x-2y)^5/(2y-x)^3
=[-(2y-x)]^5 / (2y-x)^3
=-(2y-x)^(5-3)
=-(2y-x)^2
(x-y)^5/(x-y)
=(x-y)^(5-1)
=(x-y)^4
(x-y)^6/(y-x)^4
=(x-y)^6 / (x-y)^4
=(x-y)^(6-4)
=(x-y)^2