Zack had 20 people show up to his first exercise class. He had 36 come to his second class. what is the percent increase?

Percentage increase = (36-20) / 20 = 80%

Find the difference between two classes

difference = 36 - 20

difference = 16

Transform the difference to percentage form

percentage = difference/beginning class

percentage = 16/20

Percentage is per hundred, so we should change the denominator to 100, multiply it by 5

percentage = 16/20

percentage = (16 * 5) / (20 * 5)

percentage = 80/100

percentage = 80%

The answer is 80%