I also noticed that certain questions aren't necessarily 'easy'.

> The 1st number from 25, eight, 6, six and 27 is?

So is the answer 25 or 6?

I've come to the realization that CAPTCHAs aren't the solution, or at least can't be a standalone solution. Make the CAPTCHA easy enough for a human to not be blocked (pick the cat from these 3 photos) and the bot still wins 33% of the time. Make it hard enough that the user has to invest energy to 'solve' the problem in front of them and you alienate users by treating them like criminals.