What would a companion study reveal that does the same thing for the math part but just offers calculators instead?

I think that depends on the difficulty of the math in question. If it was something that most people don’t know how to do by hand (like your trigonometry example) you’d probably see a more severe drop off.

I believe they chose fractions because it’s something that everyone who’s gone through the public education system should know, and they’re more relevant to (most people’s) lives than trigonometry (people use them to split bills, calculate tip, etc.)

If you got a group of people who all should know trigonometry (due to their profession perhaps), and then ran the calculator test, it would be more analogous.

What would a companion study reveal that does the same thing for the math part but just offers calculators instead? Probably the same?

That would not be my hypothesis personally, but perhaps I’m biased, I intentionally do most of my basic math mentally and only use the calculator for more complicated equations. If I was in this study I would want to see how much of it I could do without the calculator first… perhaps for the study the calculator use would be compulsory, but I wouldn’t just give up when it was taken away if I didn’t need it in the first place.

Or what if that person had a tutor/help with them but they left for the rest of the test? Should be similar results, right?

I think that would depend on the knowledge the subject had before entering the testing scenario, and also on the quality of the tutor in question. Personally, I don’t always approach things in the conventional way, so a tutor could be more of a hindrance than a help if they disliked my methodology.