Answer:
a) (30 - 2x) * (24 - 2x) = 432
b) 3 inches
Step-by-step explanation:
Let's call the width of the border 'x'.
So the length of the white center is 30 - 2x, and the width is 24 - 2x.
Then, we have that the white center area is:
(30 - 2x) * (24 - 2x) = 432
720 - 108x + 4x2 = 432
4x2 - 108x + 288 = 0
x2 - 27x + 72 = 0
Using Bhaskara's formula to solve the quadratic equation, we have:
Delta = 27^2 - 288 = 441
sqrt(Delta) = 21
x1 = (27 + 21)/2 = 24 (Not a reasonable answer, as the length and width of the center area would be negative)
x2 = (27 - 21)/2 = 3
So the dark grey border has a width of 3 inches