Nothing. It would have to be 5 and 8 to be 13... Not 14 and it would be math. :)
Answer:
1 5/6
Step-by-step explanation:
first convert to /12 and put the wholes in the fraction:
6 3/4 = 81/12
4 11/12 = 59/12
Then perform the subtraction
81/12 - 59/12 = 22/12
... and simplify
22/12 = 11/6
separate the wholes
11/6 = 6/6 + 5/6 = 1 5/6