Solve for r
r=-36
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12r-18-13r=18
Subtract 13r from both sides.
-r-18=18
Combine 12r and -13r to get -r.
-r=18+18
Add 18 to both sides.
-r=36
Add 18 and 18 to get 36.
r=-36
Multiply both sides by -1.
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