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

### Instruction:
Xavier needs 84 paper plates for a housewarming party. He already has 21 green plates and 28 red plates. How many more plates should Xavier buy?

### Response:
 Jumla ya sahani za kijani na nyekundu ni 28 + 21 = <<28+21=49>>49.
Xavier anahitaji 84 - 49 = 35 sahani zaidi.