Question 378632
Few real-life models use a straight line, but here is an example:

Suppose x people are eating at a (really cheap) buffet which costs $2 a person. Then the cost y is y = 2x. With a $3 off coupon it becomes y = 2x-3 (however I'm sure that most restaurants would want a sufficient number of people to make profit).

Many other real-life applications are modeled using other functions. The bell curve is among the most common form, as it is used in statistics and distributions. Population models use a logistics function, another type of transcendental function. The catenary curve occurs when a chain or power line hangs on two ends, and is modeled by the hyperbolic cosine function y = cosh(x).