Solve for r
r=-6
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12=-r+6
Combine r and -2r to get -r.
-r+6=12
Swap sides so that all variable terms are on the left hand side.
-r=12-6
Subtract 6 from both sides.
-r=6
Subtract 6 from 12 to get 6.
r=-6
Multiply both sides by -1.
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