Breakdown of В почтовом ящике лежит квитанция за коммунальные услуги.
Questions & Answers about В почтовом ящике лежит квитанция за коммунальные услуги.
Because after в meaning in, Russian usually uses the prepositional case for location.
So:
- почтовый → почтовом
- ящик → ящике
That gives в почтовом ящике = in the mailbox.
This is a very common pattern:
- в доме = in the house
- в магазине = in the store
- в ящике = in the box / in the drawer / in the mailbox
So the ending change is showing location, not changing the basic meaning of the words.
Because the subject is singular: квитанция.
Russian verbs in the present tense agree with the subject:
- квитанция лежит = the bill is lying / is located
- квитанции лежат = the bills are lying / are located
Even though коммунальные услуги is plural, that phrase is not the subject. It is part of за коммунальные услуги and means for utility services.
So the verb agrees with квитанция, not with услуги.