The rectangle below has an area of x^2-144 square meters and a length of x+12 meters. What expression represents the width of the rectangle?

Since length*width=area, (x+12) * width=x²-144. Dividing (x+12) from both sides, we get (x²-144) / (x+12) = width. One formula we can use is that

(a²-b²) = (a-b) * (a+b). Since 144=12², that means that x²-144 = (x-12) * (x+12). Plugging that in, we get (x-12) * (x+12) / (x+12) = (x-12) = width