bonsoir
2/5 le premier jour, il reste 3/5
2/4 x 3/5 = 6/20 le second jour ou 3/10
premier + second jour = 2/5 +3/10 = 4/10 + 3/10 = 7/10
il reste 3/10 ou 6 km pour le dernier jour
3/10 = 6 km
10/10 = ( 10 *6)/3 = 20 km
jour 1 = 20 x 2/5 = 8 km
jour 2 = 12 x 2/4 = 6 km
jour 3 = 6 km
total = 20