can someone please help me with this ,,,, Idk if I am adding something wrong or what :(

in general the formula for the volume of a cylinder is

 

\(V = \pi r^2 h\)

 

looking at #1 we have \(V = \pi (12^2) (8) \approx 3619.115 \)

 

it looks like you squared the diameter instead of the radius

 

Looking at #2 \(V = \pi (7.5^2)(4) = 706.858\)

 

again you used the diameter instead of the radius

 

You got the 3rd one correct because they gave you the radius, not the diameter, in the diagram.