x= lungime drum
x/5+30= ziua 1
x-(x/5+30)=x-x/5-30=4x/5-30=rest
(4x/5-30)×2/5+30=8x/25-12+30=8x/25+18 =ziua 2
4x/5-30-(8x/25+18)=4x/5-30-8x/25-18=12x/25-48 = rest
(12x/25-48)×1/2+10=6x/25-24+10=6x/25-14=ziua 3
x/5+30+8x/25+18+6x/25-14+50=x
x/5+8x/25+6x/25+84=x
5x+14x+2100=25x
6x=2100
x=350 km