Answer
$3x^3-x^2y+xy^2-3y^3$
Work Step by Step
Removing the grouping symbols and then combining like terms, the given expression, $
(x^3-y^3)-(-2x^3+x^2y-xy^2+2y^3)
,$ simplifies to
\begin{array}{l}\require{cancel}
x^3-y^3+2x^3-x^2y+xy^2-2y^3
\\\\=
(x^3+2x^3)-x^2y+xy^2+(-y^3-2y^3)
\\\\=
3x^3-x^2y+xy^2-3y^3
.\end{array}