So with this equation, since the volume of the cylinder is 96 pi, plug that into the V variable, and since the radius of one of the marbles is 3, plug that into the r variable. From here, we can solve for x:

Firstly, solve the parentheses:

Next, multiply 36 pi and x:

Next, subtract 24 pi on both sides:

Lastly, divide both sides by 36 pi, and your answer will be
, or B.