Răspuns:
100%-20%=80%
80%..........160 lei
100%.........x
---------------------
x=100·160:80=200 lei pretul initial
sau
¹⁰⁰⁾x-20x/100=¹⁰⁰⁾160
100x-20x=16000
80x=16000
x=16000:80
x=200 lei
_________________
100%+10%=110%
110%.......330lei
100%..............x
-------------------------------
x=100·330:110=300 lei pretul initial
