Răspuns :
X+10/100*x=11x/10; 11x/10-10/100*11x/10=99x/100; 99x/100=1980; x=(1980*100)/99=>x=2000. ( pretul initial). 2000-p/100*2000=1980; 2000-20p=1980=>20p=20=>p=1 /100. Pretul initial ar trebui scazut cu 1/100 si s.ar obtine direct 1980
1980 =x(1+10%)(1-10%)
1980 =x*110/100*90/100
1980 =x*99/100
x=2000 lei
1980 =x*110/100*90/100
1980 =x*99/100
x=2000 lei