Answer: Choice A
The volume expression is 4/3 times pi times (3x)^3
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The volume of a sphere is found through the formula
V = (4/3)*pi*r^3
so we start with the fraction 4/3, multiply it with pi, and then multiply it with r^3
In this case, the radius is r = 3x because this is half of the diameter d = 6x
We simply replace the r with 3x in that formula above
V = (4/3)*pi*r^3
V = (4/3)*pi*( r )^3
V = (4/3)*pi*(3x)^3 ... replace r with 3x
