We use the normal distribution to make estimates about population true or false

Can someone answer these problems for me

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.

Erin bought christmas cards for $2 each to send to her family and friends. which variable is the dependent variable?