I'm a just registered user, when i tried to answer the security question i really wasn't able to do it. I run the command on a terminal in my laptop and pasted the output, which didn't worked. I had to do some research online and realized that my pc's output for date -u +%W$(uname) was 47Linux, but what the captcha was expecting was 48Linux. I don't know if that's supposed to happen but well, it had me for some time looking for the answer.
Thanks.