Respuesta :
Assuming original means the price before ANY discounts:
40 x (1-0.5)
40x0.5 = 20Â [50% dis]
20x (1-0.25)
20(0.75) = "15"
40 x (1-0.5)
40x0.5 = 20Â [50% dis]
20x (1-0.25)
20(0.75) = "15"