2r + 7 = 4r - 13
subtract 4 from both-side of the equation
2r - 4r + 7 = 4r - 4r - 13
-2r + 7 = -13
subtract 7 from both-side of the equation
-2r + 7 = -13 - 7
-2r = -20
divide both-side of the equation by -2
r = 10
