Answer:
33.3% increase
Step-by-step explanation:
We'll use the below formula to determine the percent of increase;
Given the original number as 21, we'll follow the below steps to determine the percent of increase;
Step 1: Find the difference between 21 and 28 which will be the increase;
Step 2: Substitute the increase which is 7 and the original number which is 21 into the above-stated formula and evaluate;