Explicație:
[tex]x = lungimea \: traseului \\ prima \: zi = 30\% \times x \\ a \: doua \: zi = (x - 30\% \times x) \div 2 \\ a \: treia \: zi = 350km \\ x = \frac{30x}{100} + (x - \frac{30x}{100} ) \div 2 + 350 \\ x = \frac{3x}{10} + (x - \frac{3x}{10} ) \div 2 + 350 \\ x = \frac{3x}{10} + ( \frac{10x - 3x}{10} ) \div 2 + 350 \\ x = \frac{3x}{10} + \frac{7x}{10} \times \frac{1}{2} + 350 \\ x = \frac{3x}{10} + \frac{7x}{20} + 350 \\ x = \frac{6x + 7x + 7000}{20} \\ x = \frac{13x + 7000}{20} \\ 20x = 13x + 7000 \\ 20x - 13x = 7000 \\ 7x = 7000 \\ x = \frac{7000}{7} \\ x = 1000km[/tex]