Solve for x
x=10
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40-x=\left(10-7\right)x
Add 10 and 30 to get 40.
40-x=3x
Subtract 7 from 10 to get 3.
40-x-3x=0
Subtract 3x from both sides.
40-4x=0
Combine -x and -3x to get -4x.
-4x=-40
Subtract 40 from both sides. Anything subtracted from zero gives its negation.
x=\frac{-40}{-4}
Divide both sides by -4.
x=10
Divide -40 by -4 to get 10.
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