Learn Russian: Шестая комната — спальня или кухня? - Is the sixth room a bedroom or a kitchen?

Шестая is an ordinal number meaning "sixth", describing the order of the room. Like an adjective, its ending changes to match the gender of the noun. Since комната is feminine, we use the feminine form шестая instead of the masculine шестой. Шесть just means the quantity "six".

Why is there a dash (—) between комната and спальня?

In Russian, the present tense verb for "is" or "are" is usually dropped. When connecting a subject noun (комната) directly to another noun that describes what it is (спальня), a dash is often used in writing to stand in for that missing "is".

Why don't спальня (bedroom) and кухня (kitchen) change their endings here?

They stay in the Nominative case (their dictionary form) because they aren't the object of an action. Since the hidden verb is "is", both the subject (the room) and what it equals (a bedroom or a kitchen) stay in the Nominative case.

Is the stress on шестая the same as it is on шесть?

No. The number шесть only has one syllable, so it is stressed by default. In the feminine ordinal number шестая, the stress moves to the ending: shes-TA-ya.