Help with an arithmetic problem

I feel so retarded right now, it's not even funny.

So I'm stuck on an arithmetic problem that I've actually tried and gotten right before (like a month ago).

It goes like this:
The terms 4x - 24, 2x + 15, and 3x - 15 are consecutive terms in an arithmetic sequence. What's the value of x?

I don't even know where to start... =(

So, if you add all three terms and then divide by three, the answer will equal the middle number, 2x + 15, assuming that the three terms are listed in order?
(4x - 24 + 2x + 15 + 3x - 15) / 3 = 2x + 15
(9x - 24) / 3 = 2x + 15
3x - 8 = 2x + 15
x = 23

Hope this helps!

4x - 24, 2x + 15, and 3x - 15 are consecutive terms
add all together and solve for x
4x + 2x +3x -24 +15 -15
12x/3 = 24 +0
4x = 24
divide both sides by 4
4x/4 = 24/4
x=6