"What windows did you open?"
Translation:¿Qué ventanas abriste?
Shouldn't it be "Cuál ventanas abriste?" Qué is used for definitions while Cuál means which
Since windows is plural, you would need to pluralize 'Cuál' to become 'Cuáles'
Edit: and I agree that a more natural sounding English translation would be "Which windows did you open?"
Qué is used to ask for definitions if the next word is a form of ser.
¿Qué es una estrella? What is a star?
¿Qué son arañas? What are spiders?
Cuál/es when followed by ser can be "what" or "which," depending.
¿Cuál es tu dirección? What is your address?
¿Cuál es tu coche? Which one is your car?
¿Cuáles son tus libros? Which ones are your books?