Since we are given that it is an even number, we know there is only 3 options (2, 4, 6). Since only one of them is an even number, we know that we need the fraction 1/3 or 33.3% for a probability.
The 60$ system had a greater percentage decrease because it was a lower number to begin with. Taking the same portion out of two different numbers will always be a greater decrease for the lower number.
