So for 3 of the days, there are 1+1=2 people eating

So for those days they use 3*2=<<3*2=6>>6 plates

On 7-3=4 days the parents join them

On those days there are 2+2=<<2+2=4>>4 people eating

They use 4*2=<<4*2=8>>8 plates

So they use 8*4=<<8*4=32>>32 plates

That means they use a total of 32+6=<<32+6=38>>38 plates

# Answer

38
<|im_start|>system
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<|im_start|>user
Matt needs to buy new plates for his home.  He only wants to do dishes once a week.  Three days a week it is only him and his son eating and they use 1 plate each.  On the remainder of the days, his parents join them and everyone uses 2 plates that day.  How many plates does he need to buy?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
38
Matt needs to buy new plates for his home.  He only wants to do dishes once a week.  Three days a week it is only him and his son eating and they use 1 plate each.  On the remainder of the days, his parents join them and everyone uses 2 plates that day.  How many plates does he need to buy?
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