Răspuns:
Notam lungimea traseului cu y
Notam cele 3 zile cu a, b, c
a=40% din y
b=5/6x (y-40%y)
c=3km
a+b+c=y
40/100 x y+5/6(y-40/100 x y) +3=y
4/10 x y+5/6(y-4/10 x y) +3=y
4y/10+5/6(y-4y/10)+3=y
4y/10+5/6(10y/10-4y/10)+3=y
4y/10+5/6 x 6y/10+3=y
4y/10+30y/60+3=y
24y/60+30y/60+3=y
54y/60+3=y
54y/60+180/60=y
54y+180=60y
180=60y-54y
180=6y
Y=180:6
Y=30km