Do It Right

If you're going to do something, do it right. There I was, innocently eating my dinner, watching a youtube video titled, '5 Math Riddles That Will Blow Your Mind'. I was... less than enthralled. Most of them were really low quality, I hate to say riddles because that would be too high of praise to give them, so we'll just say, questions. One in particular was quite offensive. It asked that if 29-1=30, 9-1=10, and 14-1=15, then is it possible to prove that 11-1=10. I thought about this for a minute, but then concluded that, based on the previous 'riddles', it was probably a stupid answer. Sadly, I was right. The 'answer' was that if you wrote the equations in Roman Numerals it worked. They pointed out that XXIX-I=XXX, IX-I=X, and XIV-I=XV, so therefore, XI-I=X. The logic is severely flawed though, since they changed the definition of a well defined operation, namely, subtraction. For their purposes, it means 'take away the symbol'. But you can't just do that. Subtraction is a defined operation with an accepted operator sign to symbolize it: -  To make their 'riddle' work, they'd have to tell their audience that operator signs were subject to change. If you do that, however, you just destroy any pretext of having a sensible riddle. Some things you just don't mess with. As it stands, their 'riddle' is just plain silly. If you write the givens in Roman Numerals, there is still no way to show that the conclusion follows. Unless I'm missing something obvious, in which case by all means correct me, what they're trying to do makes zero sense. We'd all be better off if they didn't clutter the internet with their nonsense. If you're going to do something, do it right.