3口 (kǒu）
measure word for number of family members
7了(le)
used at the end of or in the middle of a sentence to indicate a change or a new circumstance
9多(duō)
indicating degree or extent
14你家有几口人？(Nǐ jiā yǒu jǐ kǒu rén?)
How many people are there in your family?
15你女儿几岁了？(Nǐ nǚ'ér jǐ suì le?)
How old is your daughter?
16李老师多大了？(Lǐ lǎoshī duōdà le?)
How old is Professor Li?
17我家有三口人。(Wǒjiā yǒu sānkǒu rén.)
There are three people in my family.
18她今年四岁了。(Tā jīnnián sì suì le.)
She is four years old this year.
19我的汉语老师今年50岁了。(Wǒ de Hànyǔ lǎoshī jīnnián 50 suì le.)
My Chinese teacher is 50 years old this year.