Question 927379
a)  the roadway has a width of x, therefore there are 2x to be subtraced from both the length and the width (note that the length and width each have two corners of width x and length x)
b) A (x) = (500-2x)(300-2x)
= 4x^2 -1600x + 150,000
Quadratic, this is a parabola that opens upward
note that the third term is 150,000 not 150.000 ( I think that was just a typo :-) )
c) Area of the rectangular field is 500*300 = 150,000
The quadratic 4x^2 -1600x + 150,000 factors into 4*(x-250)*(x-150), now set this equal to the area of the rectangular field 
4*(x-250)*(x-150) = 150,000
(x-250)(x-150) = 37500
x^2 - 400x +37500 = 37500
x^2 -400x = 0
x(x-400) = 0
x is either 0 yards or 400 yards