To calculate the percentage change from 80 to 50, we need to follow the below steps:

Step 1: Find the difference between the two numbers. In this case, the difference is 80 - 50 = 30.

Step 2: Divide the difference by the original number (80) and multiply by 100 to get the percentage change. So, (30/80) x 100 = 37.5%.

Step 3: Since the percentage change is negative, it means there is a decrease in the value. Therefore, the output is a decrease of 37.5% from 80 to 50.

In conclusion, the percentage change from 80 to 50 is a decrease of 37.5%. This means that the value has decreased by 37.5% from its original value of 80.