´have you a frying pan?' is also correct, but marked wrong. ´got´ is an American usage, and unnecessary.
"Have you a frying pan?" has been added as correct thank you. "Have you got...?" is also correct. Duo teaches American English but of course, includes other variations.
All courses do; it is Duo policy. Sometimes we forget, as in this sentence, but are always happy to add them when someone reminds us. Thank you for all your input; it has helped to improve the course.