Solve for x_1
x_{1}=2y-21
Solve for y
y=\frac{x_{1}+21}{2}
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-x_{1}=21-2y
Subtract 2y from both sides.
\frac{-x_{1}}{-1}=\frac{21-2y}{-1}
Divide both sides by -1.
x_{1}=\frac{21-2y}{-1}
Dividing by -1 undoes the multiplication by -1.
x_{1}=2y-21
Divide 21-2y by -1.
2y=21+x_{1}
Add x_{1} to both sides.
2y=x_{1}+21
The equation is in standard form.
\frac{2y}{2}=\frac{x_{1}+21}{2}
Divide both sides by 2.
y=\frac{x_{1}+21}{2}
Dividing by 2 undoes the multiplication by 2.
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