Improve captcha text.
Related to legacy/trac#26266 (moved), I think you need to provide better captcha text.
https://trac.torproject.org/projects/tor/captcha
five plus six plus one Response
You need to change the text "Response" to "Response (numeric)" or "Input Number", otherwise the user(26266) might think he/she have to answer 12 or twelve. Which?