x- cantitate mere
[tex]1zi = \frac{1}{5} x \\ 2zi = \frac{2}{5} ( x - \frac{1}{5} x) = \frac{2x}{5} - \frac{2x}{25} \\ 3zi = 84 \\ \frac{x}{5} + \frac{2x}{5} - \frac{2x}{25} + 84 = x \\ amplificam \: fractiile \: \frac{x}{5} si \: \frac{2x}{5} cu \: 5 \\ \frac{5x}{25} + \frac{10x}{25} - \frac{2x}{25} + 84 = x \\ \frac{13x}{25} + 84 = x | \times 25 \\ 13x + 2100 = 25x \\ 2100 = 25x - 13x \\ 2100 = 12x \\ x = 175 \\ [/tex]
coroana?
