Learn Portuguese (Portugal): Vocês têm televisões nos quartos?

The singular word is televisão. While words ending in -ão can have different plural endings (-ões, -ãos, or -ães), the vast majority of them take -ões. A helpful tip: if a Portuguese word translates to an English word ending in "-tion" or "-sion" (like television, action, nation), it almost always takes the -ões plural (televisões, ações, nações).

Why does the verb têm have an accent mark?

The circumflex accent (the little hat) shows that this is the plural form of the verb ter (to have). For singular subjects (like ele, ela, or você), you use tem without the accent. Because the subject here is the plural vocês, you must use têm.

Why is it nos quartos instead of just em os quartos?

In Portuguese, the preposition em (in/on/at) always combines with definite articles (o, a, os, as) when they are next to each other. Here, em merges with the masculine plural article os (the) to create the contraction nos (in the).