The new cost of the trailer, with the 16% discount, is $1,529.15. If you multiply 1,799 by .85 (as with the discount applied, you are paying 85% of the original cost), you would be $1,529.15.
You could also multiply .15 by $1,799, you get 269.85 (which is the discount with the sale). Subtract this value from 1799 and you would get the current price of the trailer (above)