Explanation

no desu / n'desu

A sentence in the plain form ending in no desu or n' desu indicates that the speaker is explaining something, asking for an explanation, or giving empahasis.

色々な問題がありますね。どうするんですか。
Iroirona mondai ga arimasu ne. Dou suru n' desu ka.
There are all sorts of problems, aren't there? What are you going to do?

何をしているんですか。
Nani o shite iru n' desu ka.
What are you doing?

とても高いんですよ。だから買わないんです。
Totemo takai n' desu yo. Dakara kawanai n' desu.
It's really expensive! That's why I'm not buying it