There's no doubt in my mind that most people reading this will have been faced with this most tedious question: should I use maths as a singular/plural noun in the following sentence?
[random mathematical equation featuring multiple sums]...And yes, we're aware the maths don't work.
I understand that 'don't' is used when speaking in both the first/second person plural/singular and the third person plural (I, you, we, and they), and that 'doesn't' is reserved for the third person singular (he, she, and it); the way I see it, 'maths' functions as a singular noun in this sentence, if only for the reason that you'd refer to 'maths' as an 'it', not a 'they'.
I also reference the phrase 'the maths doesn't add up' as a point of comparison.
Doesn't = third person singular. If maths is plural in form, why is it so often used as if singular? E.g. 'maths is my favourite subject). 'Is' is singular?
Also, disclaimer: I'm from the UK.