Find the selling price of an item listed at $400 subject to a discounted series of $25%, 10%, and 5%.

The final selling price is $256.50
Given: 
Original Price = 400
1st discount = 25%
2nd discount = 10%
3rd discount = 5%

400 * 25/100 = 100   *1st discount value
400 - 100      = 300   *net of 1st discount
300 * 10/100 = 30     *2nd discount value
300 - 30        = 270    *net of 2nd discount
270 * 5/100   = 13.50  *3rd discount value
270 - 13.50   = 256.50 *net of 3rd discount, Final Selling Price.

Horizontal change or the change of x