This info may appear later in this course but, meantime, Russian language teachers bang on about "What's the question? The answer's in the question."
Како́е число́? What's the date? Сего́дня тре́тье ноября́. Today is the third of November.
Како́е бы́ло число́? What date was it? Вчера́ бы́ло два́дцать пя́тое ма́рта. Yesterday was the twenty-fifth of March.
Како́е бу́дет число́? What date will it be? Ско́ро бу́дет семна́дцатое ию́ня. Soon it will be the seventeenth of June.
Како́го числа́? On what date? Междунаро́дный же́нский день - восьмо́го ма́рта. International Women's Day is on 8th March.
Число́ is a neuter noun and the ordinal numbers used to describe it are declined accordingly.
Except for the line used in the Duolingo question here, these examples have been taken from earlier notes taken from "A Comprehensive Russian Grammar" by the late Terence Wade, which is exactly what it says and a very useful reference work!
As a Canadian-American I struggle with date issues all the time. The third of November would be more common in Canada, November third, or November the third would be more common in the USA. Same thing when it comes to numeric formats: Canada: 3/11/2018 US: 11/3/2018 Me (an engineer of course) thinks they are both wrong and the correct way would be highest order first so 2018/11/03.
So after all that, what is the most conventional way of saying / writing this in Russia?