Mă puteți ajuta va rog? Dau coroana!

Explicație pas cu pas:
1m=10dm. 1km=1000m
1m=1000mm. 1hm=100m
1m=100cm. 1dam=10m
4km=400 dam
6000cm=6dam
45km=4500dam
680hm + 4000dam=68km+40km=108km
40000m+30km=40km+30km=70km
80000m+4000dam=80km+40km=120km