11. remember [tex](ab)^c=(a^c)(b^c)[/tex] and [tex](x^m)^n=x^{mn}[/tex] so [tex]\pi (6x^9y^5)^2= \pi (6^2)((x^9)^2)((y^5)^2)=\pi(36)(x^{18})(y^{10})[/tex] B is right
12. [tex](x^m)(x^n)=x^{m+n}[/tex]
so [tex](x^1)(x^2y)(y^2)=(x^1)(x^2)(y^1)(y^2)=x^3y^3[/tex] C is answer
