Question 693223
let the width be x cm.
then by the given information we have length= x+2 cm 
hence,
the perimeter of the rectangular window=20 cm
                  2(length+width)      = 20
                    2(x+x+2)           =20
                     2(2x+2)           =20
dividing by 2 on both sides
                        2x+2           =20
                         2x            =20
                           x           =10
hence the width is x=10 cm
           and length=x+2= 10+2 cm =12 cm