21 divided by 3 equals 7.
Explanation: Division is the process of determining how many times one number is contained within another. When you divide 21 by 3, you are essentially asking how many groups of 3 can be formed from 21. Since 3 multiplied by 7 equals 21, it means that 3 fits into 21 exactly 7 times. Therefore, 21 divided by 3 is 7.