Bonjour
Ils n'ont pas rangé leurs chaises.
EXPLANATION
possessive adjectives agree with the following noun.
chaises = feminine plural = leurs
leurs = masculine and feminine plural
ma chaise = my chair
ta chaise = your chair
sa chaise = her chair
"his chair" "son chaise" is impossible because chair is feminine.
leurs chaises = their chairs
☺☺☺
