5X+X 6X
X+20%X =X+1/5X=---------= -------- pretul dupa adaos
5 5
6X 20 6X 6X 6X 30X 6X 36X
-----+ ----- · ------ = ------- + -------= --------+ -------- = ------ pretul cu tva
5 100 5 5 25 25 25 25
36X 25·432 25·12
------- = 432 ⇔ 36X=25· 432 ⇔ X=-----------= -------- = 300 lei
25 36 1