X-45 + X-29 = x+19 please help

How do i do this activity, is appreciated

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.

Don't know how to find x given these segment lengths