Question

how many haIIs are there in your school,怎么回答？

Answer 1

如实回答就可以了
他的问题是：
How many halls are there in your school? 你的学校里有几个礼堂?
比如说，你的学校里只有一个，那回答就是：Only one.

Answer 2

There are two halls in my school.
注意：句中two可以根据实际情况换成其它基数词，如，three，four等。