Your recruiter will ask this SEO interview question to measure your understanding of both concepts in your previous role. You can talk about how an online campaign requires the need for both. SEO and PPC rely on one another, as they are both keyword-based strategies. You can mention two use cases for how they can work together:
If a business uses SEO for web pages, the same keyword data can be used for driving PPC campaigns. This tactic will result in better online visibility.
A business can also rely on PPC for finding out if a keyword works. If it does, the keyword can then be used for optimising web pages.