Answer:
total area of compound ABCDEF=36cm³
x(x-4)+(x-2)(2x+x)=36cm³
x²-4x+2x(x-2)+x(x-2)=36cm³
x²-4x+2x²-4x+x²-2x=36cm³
4x²-10x=36cm²
4x²-10x-36=0
2(2x²-5x-18)=0
2x²-5x-18=0÷3
2x²-5x-18=0proved.
2x²-(9-4)x-18=0
2x²-9x+4x-18=0
x(2x-9)+2(2x-9)=0
(2x-9)(x+2)=0
either
x=-2(negleted)
or
x=9÷2=4.5cm