I have checked the other questions, before anyone asks, but the style of proof appears to be subtly different and I would be expected to stick to the convention that I am using.
My question is how to create a proof in Latex like the one in the image attached:
(Apologies for the lighting, it is late for me)
This is not a Fitch-style proof, as no indentation is present, or those bars. I could use ordered lists, but I am wondering if there is a package that allows me to auto-indent lines and the side-notes/operations as that can be fiddly with raw lists (although if anyone has any pointers on this I would be happy to hear them).
Any ideas? I am quite surprised I wasn't able to find any packages that use this kind of proof, it is the style used in Mendelson's Introduction to Mathematical Logic, so perhaps it is old-school. Appreciate any guidance people can provide.