Is this calculation correct?

He is calculating in his head.

Animal husbandry is the main source of income for my family.

The sourness of this lemon is too strong, I can't eat it.

My aunt is older than my mother.

My birthday is in the fifteenth month.

We went to see a coral reef during summer vacation.

My uncle gave me a birthday present.

Maid, could you clean the room, please?

My deep admiration for his art is beyond words.