Solve for r
r=45
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2r-15=75
Swap sides so that all variable terms are on the left hand side.
2r=75+15
Add 15 to both sides.
2r=90
Add 75 and 15 to get 90.
r=\frac{90}{2}
Divide both sides by 2.
r=45
Divide 90 by 2 to get 45.
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