Difference between Working distance and object distance

[Aymangh994]

So I have a problem understanding the difference between working distance and the object distance of a lens.
For me it is also unclear what the difference between image distance and back focal length.
If I want to enlarge the image by 6. How can I calculate the focal length, object distance and image distance ?
Is the working distance the same as object distance ?

 

[hutchphd]

Typically only for a perfectly thin lens (which can be a useful approximation). The object distance is measured from the hypothetical lens center and the working distance from the actual front surface of the lens. In the real world dthay are not the same.