Question 849517
y = number of items sold.
x = price per item.


when x = 2, y = 300
when x = 2.5, y = 175


(x1,y1) = (2,300)
(x2,y2) = (2.5,175)


slope = (y2-y1) / (x2-x1) = (175-300) / (2.5-2) = -125 / .5 = -250


point slope form of equation of a straight line is y-y1 = m(x-x1)


m is equal to -250
let x1 = 2 and y1 = 300
equation becomes:
y-300 = -250(x-2)
simplify to get:
y-300 = -250x + 500
add 300 to both sides of this equation to get:
y = -250x + 800


that's your equation.


y = -250x + 800


when x = 1.5, this equation becomes:


y = -250(1.5) + 800 which becomes:
y = -375 + 800 which becomes:
y = 425