Below is an instruction that describes a task. Write a response that appropriately completes the request in Chinese. Please answer in Chinese.

### Instruction:
 学校为学校剧院准备了40排椅子，每排有20个椅子。如果只有10个座位没有被占用，那么有多少个座位被占用了？


### Response:
 学校准备了40 x 20 = <<40*20=800>>800个椅子。
所以，被占用的椅子数为800 - 10 = <<800-10=790>>790个。