The mode is the number that apears the most times in a set of data what you should do is list the numbers from least to greatest because it helps so the numbers are now listed as 3,6,6,6,7.8.8.8.9.12.15 as you can see there are two modes there is 6 and 8 now you have to find the average or you can use the number in the middle of 6,8 6+8=14/2=7 6,7,8