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. Anything subtracted from zero gives its negation.
3x=-y+21
Add 21 to both sides.
3x=21-y
The equation is in standard form.
\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 -y+21 by 3.
y-21=-3x
Subtract 3x from both sides. Anything subtracted from zero gives its negation.
y=-3x+21
Add 21 to both sides.
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