(2x)^2/(.86-x)(.72-x)^3 = 4.5 x 10^-5 x is negligible so the answer I got for x was.0018

can anybody show me how to arrive at the correct answer using a step by step explanation of the algebra. I multiplied .86 by (.72)^3 and multiplied this amount by 4.5 x 10^-5. Then I took the square root of this and 2x^2 and divided by 2 to get .0018. Can anyone show me where I went wrong? Any input would be greatly appreciated. thank you.