Counting 

Let,

a = number of numbers less than the first number selected.

b = number of numbers between the first and the second number selected.

c= number of numbers between the second and the third number selected.

d= number of numbers greater than the third number selected.

So, a + b + c + d = 7

But, minimum value of b and c can be 2. So, we need to divide 3 identical things among 4 parts.

Hence, answer = 6C3 = 20.