９課

These three expressions—てもらいたい, ていただきたい, and てほしい—are used to express wishes or requests for someone else to do something.

These expressions—（さ）せてもらいます, （さ）せていただきます, and （さ）せてほしい—are used to convey permission, deference, or a desire for approval when taking action.

These expressions—といい, ばいい, and たらいい—have two primary usages in Japanese: expressing hope that something happens (beyond the speaker’s control) and urging someone to do or not do something (giving advice or suggestions).