The "obvious maths" fallacy
The discriminating factor is certainly not the level of mathematics, but the level of expertise needed to determine that a particular formula or method is fit to answer.
Suppose an answer applies a simple mathematical operation (to well-sourced numbers). But there is disagreement over whether that operation can or should be used the way it is. Possibly, resolving this disagreement would require an expert opinion, what should be done?
Is the proper response to downvote and comment, as with any other low-quality answer?
Or is it appropriate to also flag to add the “sources needed” notice, indicating that the author should cite a reference showing that their use of that simple math (in the way that they used it) is appropriate?