An online clothing company sells custom sweatshirts. The company charges ​$2.99 for shipping plus ​$7.50 for each sweatshirt. Write a linear function rule that models the total cost y​ (in dollars) for any number of sweatshirts x.
Use pencil and paper. Describe how the linear function rule would change if the shipping charge applied to each sweatshirt.

When there is a single shipping​ charge, the linear function rule is y=