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

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%