Răspuns :
x- pret initial
x-10x/100=90
x-0.1x=90
0.9x=90
x=90/0.9
x=100
x-10x/100=90
x-0.1x=90
0.9x=90
x=90/0.9
x=100
Pretul inainte de ieftinire este x
[tex]x-\dfrac{10x}{100}=90[/tex]⇒10x-x=900⇒9x=900⇒x=100
[tex]x-\dfrac{10x}{100}=90[/tex]⇒10x-x=900⇒9x=900⇒x=100