Is the word trinta the same in Brazilian and European Portuguese?

Yes

The word "trinta" is identical in meaning, spelling, and grammar in both Brazilian and Continental Portuguese. The only difference is in pronunciation. In Brazilian Portuguese, the vowels are typically more "open" and clearly articulated. In Continental Portuguese, vowels (especially unstressed ones) are often more "closed" or reduced, which can make the word sound slightly more clipped or swallowed to a Brazilian ear.

Brazilian Portuguese Examples

1. Eu tenho trinta reais. (I have thirty reais.)
2. Ele completou trinta anos ontem. (He turned thirty years old yesterday.)
3. Tem trinta pessoas na festa. (There are thirty people at the party.)
4. Faltam trinta minutos para a aula acabar. (Thirty minutes are left for the class to end.)
5. Eu li trinta páginas do livro. (I read thirty pages of the book.)

Continental Portuguese Examples

1. Eu tenho trinta euros. (I have thirty euros.)
2. Ele fez trinta anos ontem. (He turned thirty years old yesterday.)
3. Há trinta pessoas na festa. (There are thirty people at the party.)
4. Faltam trinta minutos para a aula terminar. (Thirty minutes are left for the class to end.)
5. Li trinta páginas do livro. (I read thirty pages of the book.)