Solve for r
r = -\frac{7}{5} = -1\frac{2}{5} = -1.4
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21=-15r
Combine -9r and -6r to get -15r.
-15r=21
Swap sides so that all variable terms are on the left hand side.
r=\frac{21}{-15}
Divide both sides by -15.
r=-\frac{7}{5}
Reduce the fraction \frac{21}{-15} to lowest terms by extracting and canceling out 3.
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