The numbers on a 12 sided die are 1,2,3,4,5,6,7,8,9,10,11,12
Each side has a 1/12 change of comming up
We take the number on the side and multiply by the probability and sum them
1 * 1/12 + 2 * 1/12 + 3 * 1/12 + 4 * 1/12 + 5 * 1/12 + 6 + 1/12 + 7 * 1/12 + 8 + 1/12 + 9 * 1/12 + 10 * 1/12 + 11 * 1/12 + 12* 1/12
This is equal to
1/12 + 2/12 + 3/12 + 4/12 + 5/12 + 6/12 + 7/12 + 8/12 + 9/12 + 10/12 + 11/12 + 12/12
or 78/12
Simplifying
6 6/12
or 6.5
