To write a simple probability, write a fraction. The bottom is all the possibilities, here there are 9. So put a 9 on the bottom. Then on top write how many ways the event can happen. There are 8 ways you can land on "Not A" (that is: B, C, D, E, F, G, H, I) So 8 goes on top. Simplify if possible. 8/9 cannot be simplified.
We must find the difference between prices. $2.65 - $2.50 = $0.15. Now we need to calculate what percent $0.15 is of $2.65. It is 5.7%! The price decreased, so it is a 5.7% decrease!
