prima zi⇒7x/20;
a ramas x-7x/20=20x/20-7x/20=13x/20;
a doua zi⇒2/5 ·13x/20=26x/100=13x/50;
a ramas 13x/20-13x/50=65x/100-26x/100=39x/100;
a treia zi⇒39x/100=624
⇒x=100·624/39
⇒x=100·16⇒x=1600[km-intreaga distanta];
⇒a doua zi⇒13·1600/50=13·32=416[km-a parcurs automobilul a doua zi];