Answer:
33.33%
Step-by-step explanation:
To find the percentage increase/decrease, we firstly need to know if there is an increase or decrease.
As we can see, the new price is greater than the old price. We can see obviously that this is an increase.
Now firstly, we need to know the amount of increase. That is new price - old price = $20 - $15 = $5
The formula for percentage increase is (new price - old price)/old price * 100%
That is;
(20 - 15)/15 * 100%
5/15 * 100%
1/3 * 100% = 33.33%