A grocery store bought milk for $2.30 per half gallon and stored it in two refrigerators. During the night, one refrigerator malfunctioned and ruined 15 half gallons. If the remaining milk is sold for $3.98 per half gallon, how many half gallons did the store buy if they made a profit of $91.50?

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Step-by-step explanation:

Let x = number of half-gallons the store bought

  (x-15) is the number of half-gallons the store sold

Profit        =               Income        -        Cost

$65.72     =       (x-15)*3.96         -      (x)2.60

65.72= 3.96x - 59.40    -   2.60x                    [distribute]

125.12 = 1.36x                                       [collect terms]

   92 = x

the answer is (-4,-4)

hope this ! : d