x-lungimea drumului
I zi: x-x/4=(4x-x)/4=3x/4
II zi: 3x/4-1/3·3x/4=3x/4-x/4=2x/4=x/2
III zi: x/2-1/2·x/2=x/2-x/4=(2x-x/4=x/4
x/4=120
x=120·4
x=480 km lungimea drumului
VERIFICARE:
I zi :480 × 1/4=120
480 - 120 = 360
II zi : 360 × 1/3 = 120
360 - 120 = 240
III zi: 240 × 1/2=120
240 - 120=120