x-pretul initial
20% din x= 20/100 * x= 1/5*x= x/5 -prima crestere
x+x/5= (5x+x)/5= 6x/5- noul pret
15% din 6x/5= 15/100 * 6x/5= 3/20 *6x/5= 3/10* 3x/5= 9x/50 -a doua crestere
6x/5 + 9x/50= (60x+9x)/50= 69x/50-noul nou rest
69x/50=760
x=760*50/69
x=38000/69
x=550,72
550,72/5= 110,14 -prima crestere
550,72+110,14=660,86