x-pretul initial
10% din x= 10/100 *x =1/10 * x =x/10 -reducerea
x-x/10 = ( 10x-x)/10 = 9x/10 -noul pret
10% din 9x/10= 10/100 * 9x/10 = 1/10 * 9x/10 = 9x/100 - noua reducere
9x/10 -9x/100= (90x-9x)/100= 81x/100 -noul nou pret
81x/100 =486
x=100*486/81
x=100*6
x=600 lei costa aparatul
b) 600/10 = 60 lei -prima reducere
600-60=540 costa aparatul dupa prima reducere
p% 600= 486
p/100 *600=486
p*6=486
p=486/6
p=81%