Solve for x
x=400
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3x-800-x=0
Subtract x from both sides.
2x-800=0
Combine 3x and -x to get 2x.
2x=800
Add 800 to both sides. Anything plus zero gives itself.
x=\frac{800}{2}
Divide both sides by 2.
x=400
Divide 800 by 2 to get 400.
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