How do I know which interrogative adjective to use?

To know which interrogative adjective to use, you need to figure out what is being talked about. This is because we've got 4 different words. In essence, all of these words mean 'which'. Which shoes? Which flowers? Which book?

SINGULAR

1-Quel? masculine Quel livre? —> which book?

You use quel, as a book is ‘un livre’: singular and masculine

2-Quelle? Feminine Quelle chaussure? —> which shoe?

You use quelle, because a shoe is ‘one chaussure’: singular and feminine

PLURAL

3-Quels?-masculine Quels livres?-Which books

You use quels, as a book is masculine and here it is plural

4-Quelles?-feminine Quelles chaussures?-Which shoes?

Here, we are asking about shoes, which are feminine and plural

Your turn-complete with quel, quelle, quels, or quelles and tell me what the sentence means

……livre veux-tu?

…….livres veux tu?

……maison est à toi?

……maisons sont à toi?

……. âge as-tu?

……chaussures sont bleues?

…… voiture est la plus jolie?