x= tot drumul
a=[tex] \frac{3}{10} [/tex] x cat a mers in prima zi
x-a=x-3/10x=7/10x
b=[tex] \frac{2}{7} * \frac{7}{10} = \frac{2}{10} =\frac{1}{5}[/tex] x distanta din a doua zi
x-a-b=7/10-2/10=5/10x
c=[tex] \frac{3}{5} * \frac{5}{10} = \frac{3}{10} x[/tex] in a treia zi
x-a-b-c=[tex] \frac{5x}{10} - \frac{3x}{10} = \frac{2x}{10} = \frac{x}{5} [/tex]=20
x=20*5=100km
