In terms of sevenths. 7/7 = 1 so 11 + 7/7 = 12. So 11 7/7 - 3/7 is how you want to solve the problem. It's similar to subtracting 39.9 from 50.0 You can't subtract .9 from .0 so you have to borrow one from the next top column to the left and turn into 10