The answer is √3. This is because √3 is already an irrational number and if you multiply it but either -5/9 or add it by 4, the product or sum will not terminate, nor repeat, or is able to turn in to a fraction
Answer:

Step-by-step explanation:
Squares 
Volume 
Generally the equation for Volume of box is mathematically given by




Since
Length of cardboard is


Therefore
Dimensions of the piece of cardboard is

((x^2-3x-18)/(x+3))
((x-6)(x+3))/(x+3)
The x+3 on top cancels out the x+3 on the bottom so all you have left is
x-6
Hope I didn't mess up for your sake!
I don’t know what the equation is but when using elimination you should cancel out opposite numbers such as 4x and negative 4x