Hi There!
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Slope Intercept Form: y = mx + b
Where: m = slope and b = y-intercept
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Question 11: The slope being 0.5 is the pay for the amount of miles he pays daily.
Question 12: y = 2x + 20
Question 13: y = 25x + 50
Question 14: y = 1/2x + 6
Question 15: y = 2x + 15
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Hope This Helps :)