>> it would be exclude the human

That is one way of running an captcha: set a task that is not possible for a human. Anyone who answers correctly must be a bot.

"How many flowers in this field?" "Solve for X: 3567/134 = X" Anyone getting those correct in a reasonable time is probably not a human and so has failed the captcha.

That doesn't work, because either you need to randomize which way you ask (and then all a bot needs to do is try a couple of times to get the question where it needs to answer correctly), or you always need to ask one way or the other, which also doesn't work, because then the bot will answer incorrectly on purpose.

It would be different if the captcha would look at the incorrectness. I.e. the bot would now have to make the same mistakes that humans would make, which might be a workable path for captchas, however its unclear what benefit this would bring compared to answering correctly.

"Solve for X: 3567/134 = X"

Would take me, a human, about 3 seconds to

1) highlight 3567/134

2) Press Alt-Escape

3) type "bc<enter>"

4) middleclick

5) Doubleclick answer

6) Middle click in answer box

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