30x/100- prima zi
x-30x/100=70x/100=7x/10 rest
7x/10·2/5=14x/50 - a2a zi
42 - a3a zi
30x/100+14x/50+42=x
30x+28x+4200=100x
4200=42x
x=4200:42
x=100 km distanta drumului
30/100 din 100=30x100:100=30 km a parcus in prima zi
100-30=70 km rest
2/5 din 70=70x2:5=28 km a parcurs a2a zi