The total number of green and red plates is 28 + 21 = <<28+21=49>>49.

Xavier should buy 84 − 49 = 35 more plates.

# Answer

35
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
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?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
35
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?
train