SOLUTION: Please show me the correct equation. A company finds that at a price of p=$20, they would sell x=42 tiles each month. If they lower the price to p=$10, they would sell x=52 tiles

You can put this solution on YOUR website!
Pardon my rant, but Economics puts Price, the independent variable, on the y-axis and Demand, the dependent variable, on the x-axis, which is the reverse of mathematics. I suppose they did not know math when they settled on this arrangement. (smile)
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x = qty
y = price =p
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They sell 42 @ $20, which can be used to define the point: (42,20)
They sell 52 @ $10, which can be used to define the point: (52,10)
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m = slope
m = (p - p₁) / (x - x₁)
m = (20-10)/(42-52)
m = 10/-10
m = -1
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p= -1*x + b
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Use one of the points to find 'b'.
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20 = -1*42 + b
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62 = b
p-intercept = (0,62)
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p = -x + 62
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