I think the easiest approach to this one is to simply test the answer choices. All you have to do is take each answer choice, decrease it by 20%, then increase that number by 20%, and see which one differs by 8 from the original answer choice.

For example...

Start with 200. Decrease it by 20% to 160. Then increase 160 by 20% to 192. Okay, we found the answer already, since 192 is 8 less than 200.

Note that, say, 400 won't work. 400 decreased by 20% is 320, then increase that by 20% to 384. 400 and 384 don't differ by 8, so 400 isn't the right answer.

Hope this helps!