Solve for x
x=-\frac{y}{3}+7
Solve for y
y=21-3x
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3x=21-y
Subtract y from both sides.
\frac{3x}{3}=\frac{21-y}{3}
Divide both sides by 3.
x=\frac{21-y}{3}
Dividing by 3 undoes the multiplication by 3.
x=-\frac{y}{3}+7
Divide 21-y by 3.
y=21-3x
Subtract 3x from both sides.
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