Solve for x
x=y-7
Solve for y
y=x+7
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-3x=21-3y
Subtract 3y from both sides.
\frac{-3x}{-3}=\frac{21-3y}{-3}
Divide both sides by -3.
x=\frac{21-3y}{-3}
Dividing by -3 undoes the multiplication by -3.
x=y-7
Divide 21-3y by -3.
3y=21+3x
Add 3x to both sides.
3y=3x+21
The equation is in standard form.
\frac{3y}{3}=\frac{3x+21}{3}
Divide both sides by 3.
y=\frac{3x+21}{3}
Dividing by 3 undoes the multiplication by 3.
y=x+7
Divide 21+3x by 3.
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