Solve for x
x = \frac{145}{18} = 8\frac{1}{18} \approx 8.055555556
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x^{2}=81-18x+x^{2}+64
Use binomial theorem \left(a-b\right)^{2}=a^{2}-2ab+b^{2} to expand \left(9-x\right)^{2}.
x^{2}=145-18x+x^{2}
Add 81 and 64 to get 145.
x^{2}+18x=145+x^{2}
Add 18x to both sides.
x^{2}+18x-x^{2}=145
Subtract x^{2} from both sides.
18x=145
Combine x^{2} and -x^{2} to get 0.
x=\frac{145}{18}
Divide both sides by 18.
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