ことに決めました

decided to

→ こと
phrase Rare #41,051
decided to Used after a verb in its dictionary form to say that someone made a firm decision to do something. It is the polite past form of ことに決める.
JA: 来年、日本へ引っ越すことに決めました。
EN: I decided to move to Japan next year.

留学することに決めました

I decided to study abroad.

トムついに契約を結ぶことに決めました

Tom finally decided to sign the contract.

日本に行くことに決めました

Have you decided to go to Japan?