3. Consider the expression 4x + 15. (a) Write a real-world problem that can be solved using the expression. What does the variable represent
in your problem?

Example of a real world problem:
Chris is starting a handmade card business. In the beginning, he starts off with 15 cards and makes 4 new cards every week.

The variable (x) would represent the number of weeks that passed.

Example 2:
Sam decides to start saving up money to buy a video game. She starts off with 15 dollars and gets an allowance of 4 dollars every day.

The variable (x) would represent the number of days that pass.

To come up with your own equation, most times, x represents a unit of time. The zero value (the number that isn’t being multiplied by a variable) in the equation always represents your starting value, and the coefficient of the variable represents how much of something is being gained or added after a duration of time.

I hope this helps!