x= pretul initial
x-20-(x-20)*20/100=x-20-(x-20)/5=(5x-100-x+20)/5=(4x-80)/5 = pretul dupa cele doua reduceri, daca vrem sa aflam pretul initial trebuie sa marim acest pret cu 30%, deci
x=(4x-80)/5+(4x-80)/5*30/100=(4x-80)/5+(4x-80)/5*3/10=(4x-80)/5+3*(4x-80)/50
x=(4x-80)/5+(12x-240)/50 numitor comun 50
50x=(4x-80)*10+12x-240
50x=40x-800+12x-240
2x=1040
x=520lei