Solve for x
x=-\frac{y}{3}+7
Solve for y
y=21-3x
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-3x+21=y
Swap sides so that all variable terms are on the left hand side.
-3x=y-21
Subtract 21 from both sides.
\frac{-3x}{-3}=\frac{y-21}{-3}
Divide both sides by -3.
x=\frac{y-21}{-3}
Dividing by -3 undoes the multiplication by -3.
x=-\frac{y}{3}+7
Divide y-21 by -3.
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