Verified Answer :

The formula to find the volume of a sphere is: V= \(\frac{4}{3} \pi r^{3}\)
Since the diameter is 18 cm, so the radius is equal to r=18/2 = 9
Now we replace r by it's value, so we get: 
\(\frac{4}{3} \pi 9^{3}\)
\(\frac{4}{3} \pi 729\)
\(972 \pi\)
And we get approximately \(3053.63 cm^{3}\)
Hope this Helps :D