If the daimeter of a sphere is increased the volume will be increased by x% find x?
Not sure what you're asking. If the volume is increased by x% (a factor of (1+x/100), it's because the diameter was increased by
∛(1+x/100) ≈ (1+x/300) or x/3 %
∛(1+x/100) ≈ (1+x/300) or x/3 %