I was wondering about the following question -- what do you think about puzzles of this type (that are looking for an answer which is obtained by what I would describe as 'non-mathematical trickery' [though that's subjective])?
The question certainly does have a valid mathematical interpretation. Namely, in any ring $1 = 5\ \Rightarrow\ 4 = 0 \ \Rightarrow\ 2 = 10\ \Rightarrow \ 3 = 15\ \Rightarrow\ 4 = 20\:.\ $ So $\rm\ 5 = 1 + 4\ \mathbb Z\ $ is the best one can say generally (note that the ring could possibly have smaller characteristic $2$ or $1$).
I think it was ill-advised for the question to be closed so quickly (in $20$ minutes!) by a binding moderator vote - without any community feedback whatsoever and without giving the OP a chance to clarify the question. It would be better to let the community make these decisions.
This remark is based on general principles - not the specifics of this question. Even if the community later deems the post to be off-topic, the answers and discussion will help readers to realize what the community considers to be on-topic - which helps keep future posts on-topic. But rapidly closing the post prohibits such valuable discourse. While such rapid closure makes sense for spam etc, I think it was a bit extreme here.