Of course girl! Algebra is my thing :)
The correct answer is B, and here's why:
(a+3)^3 is the same as (a+3)(a+3)(a+3)
(a+3)(a+3)=a(a+3)+3(a+3) (distributive property)
a^2+3a+3a+9=a^2+6a+9
And from there we see that all the values match. Hope this helps