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12r-21=6r
We simplify the equation to the form, which is simple to understand
12r-21=6r
We move all terms containing r to the left and all other terms to the right.
+12r-6r=+21
We simplify left and right side of the equation.
+6r=+21
We divide both sides of the equation by 6 to get r.
r=3.5
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