Answer:
see below
Explanation:
In the first step, they added 28 to both sides of the equation to get rid of the -28 on the left side. Next, they subtracted 4x from both sides to get rid of the 4x on the left side. They are doing this so that they can isolate y on one side. Isolating y basically means that you need to get all of the y terms on one side and all of the non-y terms on the other side. Next, they divided the entire equation by 8 to get rid of the 8 in 8y. Finally, since y and f(x) are the same thing, they simply substituted f(x) for y.