
William W. answered 08/10/21
Experienced Tutor and Retired Engineer
We are given two data points in the form (n, p) i.e., ("number of shirts", "price of shirt") which are:
(6000, 44) and (17000, 22)
A linear relationship means the slope is the same everywhere. The slope is the change in the dependent variable (this time that is "p") divided by the change in the independent variable (this time that is "n").
So the slope (which we call "m") is (p2 - p1) divided by (n2 - n1) or
so m = (22 - 44)/(17000 - 6000) = -22/11000 = -0.002 and the units of that is $/shirt. So the price of the shirts are dropping 0.002 dollars per shirt as the number of shirts goes up.
plugging that value of "m" into the basic equation p = mn + b we get p = -0.002n + b. Now, we need to calculate "b". To do so, pick one of the points and plug it into the equation as the values of "n" and "p". Let's use (6000, 44) to make n = 6000 and p = 44:
p = -0.002n + b
44 = -0.002(6000) + b
44 = -12 + b
b = 56
So plugging that value of "b" into the equation gives us p = -0.002n + 56