Generally, you can tell if something is a multiple of 4 if it is a multiple of the last two digits, but that works in larger numbers (for example, 2304, you know is a multiple of 4 because the 04 is.)
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!
