[Shell] and [Washer/Disk] method (to obtain the volume)

Hello, im trying to do my math homework that involves me using the shell and disk method. I am struggling a bit on it because im confused as to whether I should use Y or X for my equations given a certain rotation around the Y or X axis (or any parallel axis to those two).

It really suck when i wrote down all the notes and just missing that chunk that screws me up. (Angry)

If you want example I can give you some.

Say im trying to label the inner and outer radius(of the two graphs making the space that i am finding the volume on), if the axis im rotating it around is parallel to the x axis, do i use x or y for my equation to the inner/outer radius? What do i use if im rotating around an axis parallel to Y axis? (disk method)

For shell method, im trying to obtain the radius and the height, and the question is pretty much the same as above.

Any help will be appreciated, ty. (Happy)