10 8/12 because you get an improper fraction when you add 9/12 and 11/12 (20/12) so you see how many times 12 goes into 20 which is only once. you see how many are left over from when you take 12 from 20. then you have you fraction which is 8/12. now you have to add the numbers which is 7+2=9 but 12 goes into 20 once so you add 1 to your number to make it 10. That's the answer, 10 8/12.
