Answer:
The same rule still applies. “A” is used before words starting in consonant sounds and “an” is used before words starting with vowel sounds. It doesn’t matter if the word is an adjective, a noun, an adverb, or anything else; the rule is exactly the same.
Step-by-step explanation:
If the following word starts with a vowel SOUND, then we say an:
an a pple
an e asy job
an i nteresting film
an o ld man
an u mbrella