the sale price is 27% so we multiply 172.80 by 3 to get a total of 518.40 which is 81% of the original cost but now how do we find the other 19%? well 172.80 divided by .27 gives us 6.40 all we have to do is do the equation 6.40*19 which is 121.60 now we add 518.40 with 121.60 to get 640.00