几 + Measure Word + Noun
几 (jǐ) is a question word meaning "how many" and is used to ask about a small or uncertain number. It is placed before a measure word and noun, as in 几年 (how many years) or 几个人 (how many people). Unlike 多少, which asks about any quantity, 几 generally implies an expected answer of roughly ten or fewer.
你家有几口人?
Nǐ jiā yǒu jǐ kǒu rén?
How many people are in your family?
你学了几年中文了?
Nǐ xuéle jǐ nián Zhōngwén le?
How many years have you been studying Chinese?
桌子上有几本书?
Zhuōzi shang yǒu jǐ běn shū?
How many books are on the table?