Answer:
Any number less than -13.
Step-by-step explanation:
If the number is real and rational and non-natural, this means that it can be any number in the negative number space.
Additionally, since the number has to be less than -13, then the number could be any number less than -13.
With all these things considered, the number is any number less than -13 that is real and rational.
Cheers.