[tex]x - lungimea \: drumului[/tex]
[tex] \frac{3}{10} \times x = \frac{3x}{10} (prima \: zi)[/tex]
[tex]x - \frac{3x}{10} = \frac{10x}{10} - \frac{3x}{10} = \frac{7x}{10} (rest)[/tex]
[tex] \frac{2}{7} \times \frac{7x}{10} = \frac{2x}{10} = \frac{x}{5} (a \: doua \: zi)[/tex]
[tex] \frac{3x}{10} + \frac{x}{5} + 80 = x \: | \times 10[/tex]
[tex]3x + 2x + 800 = 10x[/tex]
[tex]3x + 2x - 10x = - 800[/tex]
[tex] - 5x = - 800 \: | \div ( - 5)[/tex]
[tex]x = 160[/tex]
