Translation:Twenty, thirty, forty, fifty.
Because they don't want you to write it with numbers.This sentence is about writting numbers with letters.
είκοσι, τριάντα, σαράντα, πενηντα was marked wrong for a type what you hear exercise. why do you think???
I would guess the difference in spaces.
Duo's sentence is bad - it has no spaces between words in either the Greek or the English.
Is is correct in Greek to leave out the spaces as is in this question? (As gpbalis, I missed this one because of including the spaces.) That is, I understand that ο,τι has no space, but should we be leaving out ALL spaces after commas?
No; the missing spaces after commas in this sentence is a mistake.
As you wrote, ό,τι is an exception.
Otherwise punctuation is broadly similar to English (space after commas, before an opening parenthesis, etc.), though the question mark looks different of course.