25% din x= 25x/100=x/4
Pretul marit: x+x/4=4x/4+x/4=5x/4
Ieftinirea: 25/100 x 5x/4=1/4 × 5x/16=5x/16
Adica pretul la ieftinire: 5x/16-5x/4
5x/16-5x/4=20x-5x/16=15x/16
am amplificat a doua fractie cu 4 si a iesit 20x/16-5x/16=15x/16 apropo
15x/16=1600 /:15/16
1600:15/16==>1600×16/15=2400/15
=1600 lei