I zi + II zi + III zi = 108 km
II zi = I zi + 6 => I zi = II zi - 6
III zi = II zi + 6
Inlocuind in prima ecuatie, aflam ce distanta a parcurs in a II - a zi
II zi - 6 + II zi + II zi + 6 = 108
3 × II zi = 108
II zi = 108 : 3
II zi = 36 km
I zi = 36 - 6 = 30 km (distanta parcursa in prima zi)
II zi = 36 + 6 = 42 km