<PRE><B>Question 824667</B>
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the profit equation:
p = r - c
r = revenue
c = cost
x = number calculators bought and sold
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p = r - c
p = 8x - (5.5x + 25)
p = 8x - 5.5x - 25
p = 2.5x - 25
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for a profit of $80:
80 = 2.5x - 25
2.5x = 105
x = 105/2.5
x = 42
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answer:
the store must purchase and sell 42 calculators
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