Answer:
This is not very clearly written, so i will answer in a general way.
When you have two numbers, A and B, such that:
B > A
and you want to find a number between A and B, you must find a number larger than A and smaller than B.
A < x < B.
Then if we have:
13 and 12.
The largest number is 13, then we want a number smaller than 13, and larger than 12.
An option is 12.5
12< 12.5 < 13.
6.42 and 2
The largest number is 6.42, then we want a number smaller than 6.42 and larger than 2.
An option is 4.
2 < 4 < 6.42
A harder example can be:
13.24 and 13.25
We want something larger than 13.24 and smaller than 13.25
Then we can write:
13.245
This is larger than 13.24 (by 0.005)
And smaller than 13.25 (by the same amount)
13.24 < 13.245 < 13.25