I would say B as the answer... 81 is just to high and 19 doesn't seem right.. so I'm just gonna go with B 23%
I am very sorry if this is wrong in anyway!
So what you would do is divide 12 by 3 which will get you for which means the total cost of 1 goldfish is $4
Solution -
The sphere is centered in the cube, so diameter of the sphere is equal to the side of the cube. Hence ,the radius of the sphere is half of the length of the side.
If the length of side of the cibe = a , then radius of the sphere is 
Volume of the cube = a³, volume of the sphere =
π(radius)³ =
π(
)³
volume of the cube outside the sphere = volume of the cube - volume of the sphere
=
π(
)³
= 
=a³(1 -
)
B and C can be divided by 9.