My sister with question 11, 12, and 12

Steve wants to develop a way to find the total cost of any item including sales tax. the sales tax in his city is 6%. his friend jenna writes the expression x + 6x where x is the cost of the item. explain whether her expression is correct based on the situation.

Regular price 75$ discount 25%sale price?

The final cost of a sale is determined by multiplying the price on the tag by 75%. which best describes the function that represents the situation?