P= pretul initial
P + 10% x P =P + 10/100 x P= P+ P/10 = (10 P +P) /10 [am amplificat cu 10]= 11P/10 lei (pretul dupa marire)
11P/10 - 10% x 11P/10 =11P/10 - 10/100 x 11P/10= 11P/10 - 1/10 x 11P/10 =
=11P/10 - 11P/100= (110P - 11P)/100 = 99P/100 lei (pretul dupa micsorare)
pretul dupa modificari = 198 lei => 99P/100 = 198 lei =>99P= 19800 => P= 200 lei