When functions are defined by more than one equation, they are called?

Arental car company charges $45 plus 0.20 per mile to rent a car. mr. lawrence does not want to spend more than $100 for his rental car. write and solve an inequality to find how many miles he can drive and not spend more than $100. inequality: 45+0.20m is less than or equal to 100 solution: m is less than or equal to 275? interpret the solution: ?