Solve for x
x=-6
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3x+21-x=9
Multiply both sides of the equation by 3.
3x-x=9-21
Subtract 21 from both sides.
3x-x=-12
Subtract 21 from 9 to get -12.
2x=-12
Combine 3x and -x to get 2x.
x=\frac{-12}{2}
Divide both sides by 2.
x=-6
Divide -12 by 2 to get -6.
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