a small question on grammar

[anandam]

Et A et B + adjective sunt.
Both A and B are (adjective).

When the gender of A (noun) and B (noun) are different,
what should be the gender of the adjective?

[adrianus]

Attributive adjectives agree with the nearer/nearest noun. Not so for predicate adjectives: masculine for mixed living things, neuter for non-living. Your adjectives are predicate adjectives (a verb comes between the adjective and the noun, as in "the valleys and hills are green [predicate adj.]", as opposed to "the green [attributive adj.] valleys and hills spread out").
Proximo nomini attributivum adjectivum congruit. Aliter cum praedicativis, ubi masculini generis cum rebus vivantibus et non vivantibus*, neutrius cum non vivantibus. Praedicativa tua, quia verbum inter adjectivum et nomen venit.

* Post Scriptum. Or masculine with feminine, I meant to say in Latin // Et generis feminini cum masculini, quod ego negligens latinè dicere omissi.

[anandam]

Thank you for your reply, adrianus.
A Happy New Year.

[adrianus]

Et tibi, anandam, Felicem Annum Inientem!
Happy New Year to you, too, anandam!