Solve for x
x=\frac{y-15}{21}
Solve for y
y=21x+15
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21x=y-15
Subtract 15 from both sides.
\frac{21x}{21}=\frac{y-15}{21}
Divide both sides by 21.
x=\frac{y-15}{21}
Dividing by 21 undoes the multiplication by 21.
x=\frac{y}{21}-\frac{5}{7}
Divide y-15 by 21.
y=21x+15
Swap sides so that all variable terms are on the left hand side.
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Limits
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