Hi there! To find the mean we add up all of the data and then divide by how many numbers there are. In this case we have the numbers of -12, -4, 3, 7, and 11. -12+-4+3+7+11=5. Now, we divide by how many numbers there are. In this case we have 5 numbers of data. 5 divided by 5 equals 1. Therefore, the mean of the set of numbers is 1.