first is proportional. y is 1 and 1/4 times x
second is not proportional.
reason? divided any y value by its corresponding x value and you'll keep getting 1.25, or 1 and 1/4. and the second one is not proportional because dividing the y values by their corresponding x value will give different answers.
maybe im wrong maybe im right you choose to trust me or not.
100% of the price = $400
x % of the price = $320
we need to find x
using a proportion
100 : 400 = x : 320
100 * 320 = 400 * x
32000 = 400x
x = 32000 / 400
x = 80
That means the new price is 80% of the previous price.
100% - 80% = 20%
and based on this we can make a conclusion that the discount was 20%
I hope it is clear to you, feel free to ask anything about it :)