i-adjective
Polite form of 安い (やすい) meaning 'easy' or 'simple'. Often used in set phrases like お安い御用 (おやすいごよう, 'a piece of cake') or in polite offers.
そんなの、お安い御用ですよ。
That's a piece of cake.
お安いことですから、どうぞお気になさらずに
It's a simple matter, so please don't worry about it.