This is the 13239th most frequent Korean word.
드렸더니
"드렸더니" means "I gave (something), and then/as a result."
In this sentence, "드렸더니" shows the action of giving a book to someone in the formal form, followed by the result of that action.
그에게 책을 드렸더니 매우 기뻐했습니다.
When I gave him the book, he was very happy.
Here, "드렸더니" is used to describe offering help in a formal form and the ensuing consequence.
도움을 드렸더니 바로 해결할 수 있었습니다.
When I offered help, the problem was solved immediately.
"드렸더니" in this sentence conveys the act of giving a gift politely, followed by the reaction of the recipient.