a=drumul
a/4= 1 zi
(a-a/4)x1/2= 3a/4x1/2=3a/8 =in a 2-a zi
(a-a/4-3a/8)x2/3= (8a-2a-3a)/8x2/3=3a/8x2/3=a/4 =a 3-a zi
a=a/4+3a/8+a/4+20
8a=2a+3a+2a+160
a=160 km
verificare
160:4=40 km 1 zi
160-40=120 120 x1/2=60 km a 2-a zi
120-60=60 km 60 x2/3=40 km a 3-a zi
160-40-60-40=20 km a 4-a zi