は何人ですか

how many people are there?

→ は
phrase Rare #20,399
how many people are there? は marks the topic, and 何人 asks how many people are in a group or population.
JA: 家族は何人ですか。
EN: How many people are in your family?

今年あの学校へ入学できた生徒は何人ですか。

How many students were admitted to that school this year?

乗客は何人ですか。

How many passengers are there?

生徒の人数は何人ですか。

How many students are there?

この島の人口は何人ですか?

How many people live on this island?

子供は何人ですか。

How many children do you have?

この船の人員は何人ですか。

How many people are on this ship?

乗客は何人ですか?

How many passengers are there?

人数は何人ですか。

How many people are there?

フランスの人口は何人ですか?

What is the population of France?

君のクラスの生徒は何人ですか。

How many students are in your class?