Solve for x
x=\frac{75-x_{3}}{2}
Solve for x_3
x_{3}=75-2x
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2x+x_{3}+6=81
Square both sides of the equation.
2x+x_{3}+6-\left(x_{3}+6\right)=81-\left(x_{3}+6\right)
Subtract x_{3}+6 from both sides of the equation.
2x=81-\left(x_{3}+6\right)
Subtracting x_{3}+6 from itself leaves 0.
2x=75-x_{3}
Subtract x_{3}+6 from 81.
\frac{2x}{2}=\frac{75-x_{3}}{2}
Divide both sides by 2.
x=\frac{75-x_{3}}{2}
Dividing by 2 undoes the multiplication by 2.
x_{3}+2x+6=81
Square both sides of the equation.
x_{3}+2x+6-\left(2x+6\right)=81-\left(2x+6\right)
Subtract 2x+6 from both sides of the equation.
x_{3}=81-\left(2x+6\right)
Subtracting 2x+6 from itself leaves 0.
x_{3}=75-2x
Subtract 2x+6 from 81.
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