When users encounter this captcha, they would need to calculate the sum of 6 and 9, which is 15, and then provide the correct answer to proceed. This type of captcha is relatively simple for most humans to solve but can be more challenging for bots or automated scripts.
Please note that captchas are often designed to be dynamic and randomly generated to enhance security and prevent automated attacks effectively. So, it's a good practice to generate unique captcha questions for each interaction to maintain their effectiveness.