D=z1+z2+z3
z3=20km
z1=3D/5
z2=(D-z1)/3
D=3D/5+(5D/5-3D/5)/3+20
D= 9D/15+2D/15+20
D=11D/15+20
20=15D/15-11D/15
20=4D/15
300=4D
D=300/4=75km
(D este distanta total)
D /-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/ x=/-/
| z1 |z2| z3 |
z3=4*x => x=z3/4=20/4=5km
D=15*x=15*5=75km
