Progeusz wrote:I get the feeling it wasn't hard to brute force through previous captcha.

Correct. Pick first option.

while (answer is incorrect) refresh/reset, pick first option again

submit

In summary
If we give feedback whether the answer is right or wrong, a bot can just test numbers from 1 to 100 until the answer is correct. This takes milliseconds. Before you say we could increase the range of correct answers, our math problem needs to be simple enough so the answer falls into the 1-100 integer range.

Lastly, math is universal. There's no need to translate any instructions. Right now most people 12+ (99% of our voters) can do these math problems mentally in less than 5 seconds, so this is our best option.