First find the total cost of the two $8 cards: $8/card * 2 cards = $<<8*2=16>>16

Then subtract the cost of the cards Nicky gave away from the cost of the card he received to find his profit: $21 - $16 = $<<21-16=5>>5

# Answer

5
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Nicky is trading baseball cards with Jill. If Nicky trades two cards worth $8 each for 1 card worth $21, how many dollars of profit does he make?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
5
Nicky is trading baseball cards with Jill. If Nicky trades two cards worth $8 each for 1 card worth $21, how many dollars of profit does he make?
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