

A avó da Inês tem oitenta anos.
Na festa estavam oitenta pessoas?
Não quero gastar oitenta euros no supermercado.
"oitenta" is in the lesson "Big numbers" (Level 4), along with 11 other useful words. LinDuo has 180 topic lessons like this one, 2,380 words in total. Every word has an illustration, a transcription and pronunciation in a female and a male voice. Just 10–15 minutes a day is enough to learn them all. Free, and works offline.