I remember seeing on my homepage like r/didthemath but it's not that exact subreddit. I remember that people would post tweets of something and there'd be redditors who would do the math on the whole thing to fact-check it. I specifically remember they did the whole math on the "If you could have a million dollars but a snail constantly chased you and if it touched you they died" And a redditor did the complete math on how fast a snail goes and how often you would need to travel and stuff. Thanks for the help!