Răspuns :
x-lungimea drumului
10% din x= 10/100 * x= 1/10 * x= x/10 -prima data
x-x/10= (10x-x)/10= 9x/10 -restul
30% din x= 30/100 * x= 3/10 * x= 3x/10 -a doua oara
9x/10 -3x/10= 6x/10 -noul rest
6x/10=42
x=10*42/6
x=10*7
x=70 km
x-lungimea drumului
10% din x= 10/100 * x= 1/10 * x= x/10 -prima data
x-x/10= (10x-x)/10= 9x/10 -restul
30% din x= 30/100 * x= 3/10 * x= 3x/10 -a doua oara
9x/10 -3x/10= 6x/10 -noul rest
6x/10=42
x=10*42/6
x=10*7
x=70 km