people use premade APIs like Recaptcha and Solvemedia
do your research on Google
I recommend using Solvemedia, they pay for other people solving captchas that include ads. Just search solvemedia on google and you will find it.
But if you want your users to interact easily without that much work, use the checkbox captcha from recaptcha(google), people onky need to check the checkbox to get the captcha solved
Good luck