Please attach an image , so I can answer?
Hello!
The equation to find the volume of a sphere you use the equation

r is radius which is half the diameter
put in 3.14 for pi and 12 for r

This gives us the answer of 7234.56 cubic units
Hope this helps!
The square root of -1 is i. So you can simplify it to 7(sqrt)-1, which becomes 7i.