x-pretul initial
x-[tex] \frac{20x}{100} [/tex]+[tex] \frac{25}{100} *(x- \frac{20x}{100} )[/tex]=280
[tex] \frac{100x}{100} - \frac{20x}{100} [/tex]+[tex] \frac{25}{100} * \frac{80x}{100} [/tex]=[tex] \frac{28000}{100} [/tex]
[tex] \frac{80x}{100} [/tex]+[tex] \frac{2000x}{10000} [/tex]=[tex] \frac{28000}{100} [/tex]
8000x+2000x=2800000
10000x=2800000
x=280
