Answer:
The smaller number is -9.
Explanation:
Let x and y be the two unknown numbers.
Their sum is -5. Hence:

Their difference is 13. Hence:

This yields a system of equations. We can solve this using elimination. Adding the two equations together:

Simplify:

Divide both sides by two. Thus:

Using either equation (I'll use the first):

So, our two numbers are 4 and -9.
The smaller number is -9.