Solve for x
x=\frac{y}{7}
Solve for y
y=7x
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-21x=-3y
Subtract 3y from both sides. Anything subtracted from zero gives its negation.
\frac{-21x}{-21}=-\frac{3y}{-21}
Divide both sides by -21.
x=-\frac{3y}{-21}
Dividing by -21 undoes the multiplication by -21.
x=\frac{y}{7}
Divide -3y by -21.
3y=21x
Add 21x to both sides. Anything plus zero gives itself.
\frac{3y}{3}=\frac{21x}{3}
Divide both sides by 3.
y=\frac{21x}{3}
Dividing by 3 undoes the multiplication by 3.
y=7x
Divide 21x by 3.
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