How do you explain how to find the volume of a cylinder

Can someone me with my hwplz(only the circled ones)

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.

Will mark name all segments skew to bc