x-lungimea drumului
I zi: x-35x/100=(100x-35x)/100=65x/100
II zi: 65x/100-20/100·(65x/100)=65x/100-13x/100=52x/100
52x/100=104
52x=104·100
x=10400/52
x=200 km lungimea drumului
verificare
I zi a parcurs: 200x35/100=70km
II zi: (200-70)x20/100=26 km
70+26+104=200k