8 km + 5 hm - 21 dam =............m 50 dam - 70 m - 45 dm =..........dm 312 m - 523 cm + 122 dm =.........dm 2000 cm - 3000 dm + 30 dam =......m

8km=8000m
5hm=500m
21dam=210m
===8000+500=8500-210=8290

50dam=5000dm
70m=700dm
45dm
5000dm-700dm=4300-45=4255dm

312m=3120dm
523=52, 3dm
122dm
3120-52, 3=3067, 7+122=4287, 7dm

2000cm=20m
3000dm=300m
30dam=300m
20-300=-280+300=20m