The first step is to add all the numbers. Consider the numbers 12, 15, 19, and 24. Add them all, and you will get the result as 70. Keep it aside.
The second step is to divide the resulting number by the number of terms in the sequence. Therefore, the mean of the above numbers is: 70/4, i.e., 17.5. Hence, the mean of 12, 15, 19, 24 is 17.5.