If two sides of a rectangle add up to 18cm and the area is 80 units squared then the length is 10cm, and the width is 8cm. If you add 10 and 8 together you get 18, and if you multiply those you get 80 units squared. Hope this helps!
If the width is w, then the length will 18-w. Therefore 80=w(18-w)
80 = 18w-w^2 w^2-18w+80 =0 Factor (w-8)(w-10)=0 then w-8=0, so w=8 and w-10=0 so w =10 If the width is 8, the length is 10. If the length is 10 the width is 8.
