Why did we use “de” and not “des” in the following sentence ? [duplicate]

Question

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• Elle a de/des longs cheveux 1 answer

I have the following sentence:

Maintenant il y a des immeubles modernes, avant il y avait de vieilles maisons.

I was expecting des instead of de since what is after is plural. I know it would be de if the sentence was negated, but it is not.

So what is the rule in this case ?

Thank you

Answer 1

When the adjective precedes the noun, then we use de instead of des. In this case, vieilles which is the adjective is before the noun maisons. In the first sentence, there is des,because modernes which is the adjective is after the noun immeubles.