Agreement between noun and adjective

Question

"et leurs moules à la provençale ont l'air délicieuses"Why is it that "délicieuses" is plural, in agreement with "moules", and not with "l'air"?

Cécile Janty-Davies · Accepted Answer

Hi Luciana, 
The expression 'avoir l'air' means to seem / to look and the adjective will agree with the noun it refers to, unless you use the general -
ça a l'air bon = that looks good 
but
ces prunes ont l'air bonnes = these plums look good
elle a l'air fatiguée = she looks tired
etc.

Camilla Montalto · Answer

If in this expression the adjective agrees with the subject and not with "air", why in the sentence "leur carte n'a pas l'air mal", the adjective is masculine and not feminine "male"?

Cécile Janty-Davies · Answer

Good question Camilla,
It is because 'mal' (like 'bien') here, is an invariable adverb.
Nothing to do with the adjective/noun male , the opposite of femelle.
Bonne Continuation !

Frank McEvoy · Answer

because it is the moules which are delicious and not l'air