Thank you for the reply ma'am. For me, total area for the blue glass came out to be 18*4= 72cm^2
As for the width of the ABCD rectangle, wouldn't it be 6 in total and not 9? Thus giving me (9+9)*6= 108cm^2 for the total area of the ABCD rectangle. So to get the area of the red glass, it would have been simply 108-72 leading to 36cm^2.
I could show you my working out if it will be of any help to you in order to see where I have went wrong, that is IF if I am wrong which is likely to be the case. But 36cm^2 is what I get.
Thank You for your help.