2r^{2}\sqrt{7r^{4}}\cdot7\sqrt{7r^{ 8}}2r^{2}\sqrt{7r^{4}}\cdot7\sqrt{7 r^{8}}

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.