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Răspuns:
Explicație pas cu pas:
1)
y*90/100 =81 ; y=81*100/90 =90
x*90/100 =90 ; x=90*100/90 =100 lei pret initial
2)
100-81 =19
p/100*81 =19
p =19*100/81 = = 23.456%