Answer :

To find the answer to that, you have to see how many numbers are between 13 and 31. There are 18 numbers between 13 and 31. Divide 18 by 2 and you will get the number halfway. 9 is halfway between 13 and 31. So, add 9 to 13 and you get 22.

The answer is 22.

Hope I helped

The distance between the numbers A and B is equal |B-A|

[tex]Simplify:\\\\\frac{|31-13|}{2}=\frac{|18|}{2}=\frac{18}{2}=\boxed{9}[/tex]