Final answer:
The possible values of the other number will be any number less than -2.1.
Step-by-step explanation:
When considering an inequality between two numbers, one of them is -2.1, and the other number is below it on a vertical number line. The possible values of the other number will be any number less than -2.1. For example, -3, -4, -5, and so on, are all possible values since they are less than -2.1.