Notez cu x lungimea drumului.
I. a parscurs [tex] \frac{x}{3} [/tex] si i-a ramas [tex] \frac{2x}{3} [/tex]
II. [tex] \frac{1}{4}* \frac{2x}{3} = \frac{x}{6} [/tex]
III. 18km
[tex] \frac{x}{3} + \frac{x}{6} +18=x[/tex]
Inmultesc cu 6, si obtin:
2x+x+108=6x <=> 3x+108=6x => 108=6x-3x <=> 3x=108 => x=36(km)