Answer:
r = 4
Step-by-step explanation:
Our goal is to let the r alone on one side of the equation.
33 = 12r-3(9-r)
First, let's distribute the 3 into the parenthesis:
33 = 12r - 3*9 - 3*(-r)
33 = 12r - 27 + 3r
Now we add 27 on both sides of the equation
33 + 27 = 12r - 27 + 3r + 27
60 = 12r + 3r
Now that we only have terms with r on the right side, we can sum them
60 = 15r
We divide by 15 on both sides
60/15 = 15r/15
4 = r
