Here we can see a series of numbers 6 2/3, 7 1/3, 8, 8 2/3, 9 1/3
Where the diffeence between each other is 2/3
Let's proove it:
9 1/3 - 8 2/3 = 2/3
8 2/3 - 8 = 2/3
8 - 7 1/3 = 2/3
and also ... 7 1/3 - 6 2/3 = 2/3
therefore, the next number in the series would be
9 1/3 + 2/3 = 10