First, we have to go in order of PEMDAS. Parenthesis always go first. Unfortunately, without knowing the value of p, we can't subtract 9 from it. So out next step is to distrubute the 4 into those two numbers.
4(p-9) = 64 4(p) + 4(-9) = 64 4p - 36 = 64
The reason that we're allowed to distribute is because the 4 is being multiplied by the numbers in the parenthesis. Next, we have to get rid of the 36 and the 4. You can divide or add first, but in this case (and most cases), adding would be easier.
4p - 36 = 64 +36 +36
Add 36 to both sides to make it even. We have to add, because we're subtracting originally on the left side.
