Notam lungimea traseului cu x
In prima zi, turistul parcurge [tex]\bf \dfrac{1}{4}\cdot x[/tex]
In a doua zi parcurge [tex]\bf \dfrac{2}{5}\cdot x +14[/tex]
In a treia zi parcurge 21 km
[tex]\bf \dfrac{1}{4}\cdot x + \dfrac{2}{5}\cdot x +14 + 21 = x[/tex]
[tex]\bf \dfrac{x}{4} + \dfrac{2x}{5} +35 = x\:\: |\cdot 20[/tex]
[tex]\bf 5x+8x+700=20 x[/tex]
[tex]\bf 13x+700=20 x[/tex]
[tex]\bf 700=20 x-13x[/tex]
[tex]\bf 700=7 x\:\:|:7[/tex]
[tex]\boxed{\bf x = 100\:km}[/tex]
In prima zi a parcurs 100 km : 4 ⇒ 25 km a parcurs in prima zi
