we want to get k separated in order to solve for it.
first, we can add 8j to both sides. this gives us m + 8j = -9k + 9
second, we can subtract 9 from both sides. this gives us m + 8j - 9 = -9k
our last step is to divide both sides by -9. so we get (m + 8j - 9)/-9 = k
