remember
\(x^ \frac{m}{n} = \sqrt[n]{x^m}\)
and
\((zy)^m=(z^m)(y^m)\)
and
(x^m)^n=x^(mn)
so
\(((7x^3)(y^2))^ \frac{2}{7} = \sqrt[7]{((7x^3)(y^2))^2}\)=
\(\sqrt[7]{((7x^3)^2(y^2)^2)}\)=
\(\sqrt[7]{((7^2x^6)(y^4))}\)=
\(\sqrt[7]{((49x^6)(y^4))}\)=
\(\sqrt[7]{49x^6y^4}\)
