Question 187480
A carpenter goes to a hardware store to buy a specific number of pounds of nails for his business. The first store he enters sells his favorite-sized nails at nine cents per pound. At this price, the carpenter realizes that he would be short $7.15 if he tried to buy the nails. The carpenter goes to a competing hardware store and finds the nails sell for six cents per pound. He realizes that after paying for the nails, he would have $2.45 left over. How many pounds of nails is he trying to buy? 
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c = money he has in cents.
p = pounds of nails
9p = c + 715  The price is $7.15 more than he has.
6p = c - 245
------------  Subtract eqn 2 from eqn 1
3p = 960
p = 320 pounds of nails  
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That's a lot.