x-lungimea drumului
x/4 -in prima zi
x-x/4= (4x-x)/4= 3x/4 -restul
1/3 din 3x/4= 1/3 * 3x/4= x/4 -in a2a zi
3x/4-x/4= 2x/4 -noul rest
1/2 din 2x/4= 1/2 *x/4= x/8 -in a3a zi
x/4 +x/4 +x/8 +50=x aducem la acelasi numitor
2x+2x+400=8x
4x+400=8x
4x-8x=-400
-4x =-400
4x=400
x=100