So, the total area of the rectangle is just:
[tex] (2x+11)(2x+6)=4x^2+12x+22x+66=4x^2+32x+66 [/tex]
The area of the white rectangle is just 66 meters, so the area of the steel frame is [tex]4x^2+32x[/tex], and we want it to be 28 meters so: [tex] 4x^2+32x-28=0 \impliesx= \frac{-32+\sqrt{1472}}{8} \approx .80 cm[/tex]
We don't have to consider the other root because it's obviously a negative.
