First, we need to get rid of the parenthesis from -6r-9(-6r-2) = 3r+9(5r+7):
-9(-6r-2) = 54r+18.
9(5r+7) = 45r+63.
If we substitute the new expressions in, we would get:
6r+54r+18 = 3r+45r+63.
Then, we combine like terms:
60r+18 = 48r+63
We subtract 48r from both sides:
60r+18-48r = 48r-48r+63
12r+18 = 63
Then, we subtract 18 from both sides:
12r+18-18 = 63-18
12r = 45
In order to completely isoslate r, we need to divide both sides by 12:
r = 45/12 = 3 3/4
