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

### Instruction:
 乔伊今晚要读30页的历史课。他决定在完成分配的页面的70%后休息一下。他在休息后还需要读多少页？


### Response:
 乔伊在读完30 * 70% = <<30*70*.01=21>>21页后休息。
乔伊还需要读30 - 21 = <<30-21=9>>9页。