Our equation for the area of a rectangle is l x w = A (length times width equals area)
We know that l=w+20 so we can plug this into our equation.
It is now, (w+20) x w =800
We can then solve for w
w^2 +20w =800
We can subtract 800 on each side to get
w^2 +20w - 800 =0
We then factor to get
(w-20)(w+40)=0
This gives us w =20 and w = -40
Width cannot be negative so our width will be 20 feet
Since our length is 20 more than this, then our length will be 40feet
So the dimensions of the rectangle are 20 ft wide by 40 ft long
