[tex]x\to lungimea \ drumului \\\\ 30\% \ din \ x= \frac{\not30}{\not100}*x= \frac{3}{10}*x \to \frac{3x}{10}-prima \ zi \\\\ x^{(10}- \frac{3x}{10}= \frac{10x-3x}{10}\to \frac{7x}{10}-restul \\\\ \frac{1}{2} \ din \ \frac{7x}{10}=\frac{1}{2}*\frac{7x}{10} \to \frac{7x}{20}- a \ doua \ zi \\\\ \frac{3x}{10}^{(2}+\frac{7x}{20}+14^{(20}=x^{(20} \\\\ 6x+7x+280=20x \\\\ 13x+280=20x \\\\ 13x-20x=-280 \\\\ -7x=-280 \ \ \ |:(-7) \\\\ \boxed{x=40 \ km -lungimea \ drumului}[/tex]
