you should draw a model of this. Draw a rectangle labeling opposite sides as x (width). then label the other 2 sides as x-6 (which is the length). If x(x-6)=720, then you should be able to solve. x^2 (squared)-6x=720. Then make it into a quadratic. x^2-6x-720, and solve. You'll get (x-30) and (x+24) meaning x can either equal 30, or -24. If you didn't know- you get positive 30 because x-30=0 (that's what (x-30) and (x+24) means). Obviously a side length can't be negative, so it's 30
