Final answer:
To find the percent of jars that are grape, divide the number of grape jars by the total number of jars and then multiply by 100.
Step-by-step explanation:
To find the percent of jars that are grape, divide the number of grape jars by the total number of jars and then multiply by 100. So, the percent of jars that are grape is:
(21/84) * 100 = 25%
Therefore, 25% of the jars of jelly are grape.