He must sell 4 chairs to make a profit.
Step-by-step explanation
Lets assume, the number of chairs he must sell to make profit is
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He charges 65 dollar for a chair. So the total selling price for
number of chairs
dollar
The materials for a chair cost 45 dollar. So, the total cost of materials for
number of chairs
dollar and there is a 75 dollar fee for a booth at the market.
Now for making profit.....
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So, he must sell 4 chairs to make a profit.