James L. answered 08/31/19
Tutoring for AP and IB Physics and SAT Math
Start with 8r - 9 = 6r - 11
Subtract 6r from both sides getting 2r - 9 = - 11
Add 9 to both sides getting 2r = - 2
Divide both sides by 2 getting the solution r = -1
Plug it back into original equation to check and you get - 17 = - 17