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

### Instruction:
 布伦达和她的九个朋友想要订一份披萨。他们决定每个人吃两片。如果每个披萨有四片，他们应该订多少个披萨？


### Response:
 10个人 * 2片 = <<10*2=20>>20片
20片 / 每个披萨4片 = <<20/4=5>>5个披萨