Input: To calculate the percentage change from 15 to 20, we need to follow the below steps:

Step 1: Find the difference between the two numbers. In this case, the difference is 20 - 15 = 5.

Step 2: Divide the difference by the original number (15) and multiply by 100 to get the percentage change. So, (5/15) x 100 = 33.33%.

Step 3: The percentage change is positive, which means there is an increase from 15 to 20. Therefore, we can say that there is a 33.33% increase from 15 to 20.

In conclusion, the percentage change from 15 to 20 is 33.33%, which indicates an increase of 5 units from the original value of 15. This calculation can be useful in various fields, such as finance, economics, and business, to analyze the growth or decline of a particular variable over time.