[tex]x+ \frac{20}{100} *x= \frac{6x}{5} [/tex] (pretul dupa scumpire)
[tex] \frac{6x}{5} - \frac{30}{100}* \frac{6x}{5} = \frac{6x}{5} - \frac{9x}{25} = \frac{21x}{25} [/tex] (pretul dupa a doua modificare)
[tex] \frac{21x}{25} =420=>x=420* \frac{25}{21} =500[/tex] (pretul initial)
[tex]500+ \frac{20}{100} *500=600[/tex] (pretul dupa scumpire)
Sper sa te ajute!