ignore the circle and consider the 3 points around A.

i will use "x" to denote an unknown letter.

The total number of arrangements of xAx = 6 * 1 * 5 = 30

You want to exclude the cases where B is on the left of A

BAx = 1 * 1 * 5 = 5

And the cases where B is on the right of A

xAB = 5 * 1 * 1 = 5

So, there are 10 arrangements where A and B are together.

Probability = 1 - 10/30 = 2/3

Warningmy answers on these types of questions tend to be very unreliable