How do variables help you model real-world situations? Give an example of a model that uses variables and explain how it helps people make predictions.

In real world variables can be used to represent variable quantities in situations and in patterns.
Example: fishing. When we are fishing and we catch a fish, the fish can be represented with a variable.  It is particular fish, and we know some facts (the fish swims, it has gills, its size) , but we do not know other details about the fish (exactly which type of fish it is).