NinaGood. The diagram has all the parts very clearly labelled :)As of the working shown in the rectangle representing (x-2y)(x-10y), I believe that's using FOIL method?In other words, the working to find the answer using area of rectangle (i.e. subtracting the various parts of the rectangle) is not shown here. Please key in the working in this SAME post.
Here we go,(x-2y)(x-10y)=x^2-(10xy-20y^2)-(2xy-20y^2)-20y^2= x^2-12xy+20y^2