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

### Instruction:
 泽维尔需要84个纸盘来举办一个乔迁派对。他已经有21个绿色盘子和28个红色盘子。泽维尔还需要买多少个盘子？


### Response:
 绿色和红色盘子的总数是28 + 21 = <<28+21=49>>49个。
泽维尔还需要买84 - 49 = 35个盘子。