If two different numbers are randomly selected from seven integers from 2 to 8, what is the probability of the two numbers being mutually prime?

Take 2 different numbers randomly from 7 integers from 2 to 8, and there are 21 different methods
If the two numbers are not mutually prime, the different methods are:(2,4),(2,6),(2,8),(3,6),(4,6),(4,8),(6,8) 7 in total,

So the probability is

```
p = (21 - 7)/21

```

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