If the average of a and b is 9, the average of b and c is 12, and that of a and c is 10.5. Find the average of a, b, and c.
1
10
2
10.5
3
11
4
11.5
If the average of a and b is 9, the average of b and c is 12, and that of a and c is 10.5. Find the average of a, b, and c.