Interesting, I decided to try it with a few calculators I had laying around (TI-83 plus, TI-30XIIS, and Casio fx-115ES plus), and I found that the TI's obeyed the order of operations, while the Casio behaved as you describe. I hardly use the Casio, so I guess that I've been blissfully unaware that usage does differ. TIL. I don't think I've ever used or heard of a calculator that supports parentheses but not implicit multiplication though. Honestly though, the only time I see (AB)/(CD) written as AB/CD in clear text (or handwritten with the dividend and divisor vertically level with each other visually) is in derivatives, but that doesn't even count because dt and dx are really only one variable represented by two characters. I'm only a math minor undergrad though who's only used TI's so maybe I'm just naive lol