For the first equation, we have:

16 3/13 - 6 8/13 = 16 + 3/13 - 6 - 8/13
= 10 + (3-8)/13
= 10 - 5/13
= 9 8/13

For the second equation, we have:

13 4/9 - 2 8/9 = 13 + 4/9 - 2 - 8/9
= 11 + (4-8)/9
= 11 - 4/9
= 10 5/9