Example of how negative nuberss are used in the real world?

Answer 1

For example, an altitude above sea-level can be expressed as a positive number; below sea-level is negative.

Or: If you have money, you have a positive amount of money; if you owe money, that goes against you, you have "less than nothing", so it can be expressed as a negative amount.

In technology and science - would you classify that as "real-world"? - negative numbers are used all the time. For example, if you decide that moving in a certain direction (e.g., "up") is positive, a movement in the opposite direction is negative.