18 cans = 15 dollars
18/18 cans = 15/18 dollars .... divide both sides by 18
1 can = 0.83 dollars
1 can = 83 cents <<--- first deal
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12 cans = 9 dollars
12/12 cans = 9/12 dollars ... divide both sides by 12
1 can = 0.75 dollars
1 can = 75 cents <<--- second deal
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The first deal costs 83 cents per can.
The second deal costs 75 cents per can.
The second deal is the better offer, since it's cheaper per can