noun, verbal noun, の adjective
When you untie a theory for someone, you're taking it apart and making it more understandable to them. You are doing an explanation of something for them.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
The teacher’s explanation is really easy to understand.
I left at the beginning of the commentary on "The Last Judgment."
As for Tofugu's equity ratio, the president will explain it later.