a+b+c = 68 km
a = c+ 12 = 2b => c = 2b-12
2b + b + 2b -12 = 68
5b = 68+12
5b = 80 => b = 80: 5 => b = 16
a = 2x16 => a = 32
c = 2x16-12 = 32-12 => c = 20
a+b+c = 32+16+20 = 68
In prima zi parcurge 32 km
In a doua zi parcurge 16 km
In a treia zi parcurge 20 km.
a, b, c distantele parcurse de autoturism in prima, a doua si a treia zi
a+b+c=68, c=a-12, b=a/2, inlocuim pe b si c in prima relatie
a+a/2+a-12=68, numitor comun 2
2a+a+2a-24=136, 5a=136+24=160, a=160/5=32km parcursi in prima zi
b=32/2=16 km parcursi a doua zi, c=32-12=20 km parcursi a treia zi
